Hello everyone! I wanted to try and give back to the community by compiling all my knowledge I’ve learned about DoTs from playing/lurking the forums. There are three sections, and I’ve wrapped each in spoiler tags to avoid giant walls of text. I hope you enjoy!
Types of DoTs
Each damage type has a damage over time affect associated with it (except for a special case), and the resistance that affects a damage type also affects it’s corresponding damage over time effect. Here are the list of DoTs in Grim Dawn that follow this rule.
Physical → Internal Trauma
Fire → Burn
Cold → Frostburn
Lightning → Electrocute
Acid → Poison
Vitality → Vitality Decay
In addition, conversion mechanics also apply separately to these DoT types. For example, having a weapon with 15% of Physical damage converted to Lightning, will also cause 15% of your Internal Trauma damage to be converted to the Electrocute type. Aether and Chaos are not listed, as they do NOT have any DoT type associated with them; any Aether/Chaos conversion will NOT affect the DoT damage type (thanks DenisMashutikov!)
The one DoT that does not follow the aforementioned rules is Bleeding. One would think that the same rule would apply to Piercing → Bleeding, but this is not the case. Bleeding is its own damage type separate from Piercing, with its own resistance. Because of this, conversion mechanics do not apply to Bleeding; 15% Physical to Piercing (Armor Piercing) conversion will not convert Internal Trauma damage to Bleeding. This is important to keep in mind when planning a Bleeding damage build, as the options available to you are different than, say, a Frostburn build.
How DoTs Work
DoTs are able to stack, but only from different sources. Sources are different skills, item/devotion procs, and weapon damage. For example, Night’s Chill, Blizzard, Nightfall, and a Savagery strike applying Frostburn damage will have all of their Frostburn damages stack on top of each other. However, when an existing source is applied again, the DoT simply reapplies and does not stack on itself. In the above example, using Shadow Strike again will reset the Nightfall Frostburn DoT. HOWEVER, the Savagery strike will deal Flat Frostburn damage from the weapon damage as its source, meaning that the weapon damage component of Nightfall (around 40%) will be overridden by the weapon damage source from Savagery (since it’s much higher). (Thanks Silben!) Nightfall and skills like it actually deal two sources of DoT damage; weapon damage, and the skill itself.
Highest Damage Takes Precedence
However, given the same source, the DoT with the highest damage will take precedence. What this means is that if the DoT would happen to do more damage than the old one, it will replace it. Conversely, if the DoT would happen to do less damage, the old one will complete first before the new one takes effect.
For example, if I use a skill that deals 100 Bleeding damage/second for 3 seconds, and then step into a Wendigo Totem area and get a +50% Bleed damage buff from Blood Pact, and then use that skill again, the original DoT will be replaced with the buffed version dealing 150 Bleeding damage/second for 3 seconds. If I step out of the area and use the skill a third time, the 150 Bleeding damage/second will not be replaced and will continue until its duration has ended, whereupon the 100 Bleeding damage/second will immediately take effect.
Flat DoT Damage and “X% chance of DoT damage” or “X% chance of +X% DoT damage”
If you see a DoT damage type on a piece of equipment, a Devotion, or a passive/buff skill (e.g. Deadly Momentum, Overload) this is called Flat damage and is applied through either main hand OR off hand (if using a second weapon or a shield) damage, but NOT both simultaneously (thanks Cyrim and Coincident!). For example, the Fox devotion giving 15 Bleed damage/3 seconds will apply when I hit with my weapon or use a % weapon damage skill. Flat DoT damage will be magnified/diminished when weapon damage is magnified/diminished; if I used Cadence doing 300% weapon damage, the damage from Fox devotion will now be 45 Bleed damage/3 seconds. Since highest damage takes precedence, further strikes won’t reset this enhanced Bleed damage and it will continue to completion. This implies that when using weapon damage as a DoT source, skills that have very high % weapon damage modifiers are very useful for making the most of your Flat DoT damage, and that attack speed or cast speed are not very effective since all multiple strikes will do is refresh the Flat DoT damage.
The exception is when you have equipment/devotions/passives with “X% chance of DoT damage”, since more attack speed/cast speed means more chances to proc this effect. “X% chance of DoT damage” is a form of Flat DoT damage and is only applied to weapon damage (and skills that deal % weapon damage).
“X% chance of +X% DoT damage”, however, can apply to ANY source of the given DoT damage type. (Thanks Silben!) Gutwrench Eviscerator in particular has a very strong “15% chance of +1000% Bleeding damage” that can function as a mini-crit of sorts. This type of buff would benefit DoT builds that re-apply their DoTs quickly.
DoTs can crit when applied, and when they do the crit lasts throughout the entire duration of the effect, not just per second. This makes critical damage a particularly effective way to magnify DoT damage, and should be a priority in any DoT build.
Resistance Reduction (thanks korsar!)
DoT damage types are affected by this the same way regular damage types are, but they only check for resistance reduction when they are applied. This means that if you were to apply a DoT and then cast something like Curse of Frailty, the current DoT won’t be magnified and you’ll need to cast it again to receive the benefits. This implies that if you have any sources of resistance reduction, you should aim to apply them before casting your DoTs. Alternatively, if your DoT source has a quick cooldown, you can just apply them, use your resist reduction, and then reapply them.
When fighting reflect mobs, if they have their reflection buff up then any DoT you apply to them will apply to you instead. Because of this, make sure you have very heavy resistance to your chosen damage type OR a way to dispel your DoT (via Nullification or Ulo’s devotion ability). Internal Trauma builds in particular are very susceptible to this, as physical resistance is hard to come by, and it is recommended that builds using this DoT type go out of their way to acquire Reflected Damage Reduction (Owl, Solemn Watcher devotions as well as certain gear have this).
Breakdown of Different DoT Types
Can’t be buffed by conversion mechanics, but doesn’t really need to as it has a lot of support from gear, masteries, and devotions. Generally pretty simple to build around. Soldier and Nightblade have access to the best sources of base Bleed damage; Shaman and Occultist have access to -% Bleeding resistance while also having a few Bleed sources. Any combination of the above should yield a viable Bleeding build, although Blademaster may do worse than the other combos due to lack of -% Bleeding resistance.
Skills with highest base (per second) Bleed damage:
Transmuted Blade Arc: 344/sec
Fighting Form: 212/sec
Blade Spirit: 206/sec
Counter Strike: 171/sec
Phantasmal Blades: 170/sec
Circle of Slaughter: 142-179/sec
This is the most versatile of the DoT types, in the sense that it can be converted to other DoT types using conversion mechanics. Some of the less supported DoT types will need to rely on this mechanic to generate their base damage. That being said, Internal Trauma itself is a very strong DoT type as it has a lot of gear/skill support and does not need to worry nearly as much about bypassing enemy resistances due to its physical damage base. Remember that this also applies to you when fighting reflect mobs, so make sure you have a DoT dispel ability for yourself or reflected damage reduction. Soldier has access to some of the best sources of Internal Trauma damage while also having a Physical Resist Reduction ability, which makes it an ideal class for building around this DoT type. Secondary classes should be either Demolitionist for other great sources of IT damage, or Occultist for -% Physical Resistance. A notable downside to this DoT type is that support for % increased duration is very lacking, if not non-existent. This means that this DoT type needs much more frequent re-application, which means making yourself more vulnerable. Therefore, be sure to invest in more tankiness/survivability than you would otherwise. (Thanks Chthon!)
Skills with highest base (per second) Internal Trauma damage:
Transmuted Blade Arc – Laceration: 319/sec
Grenado – Shattering Blast: 215/sec
Forcewave – Internal Trauma: 124-170/sec
Cannister Bomb – Improved Casing: 142/sec
Stun Jacks – Full Spread: 130/sec
This DoT type got great skill support through Inquisitor this expansion. Demolitionist provides lots of Burn damage boosts while giving BWC and a few other sources, as well as -% Fire Resistance in Thermite Mines. Occultist also provides a -% Fire Resistance while having a source of Burn through the hellhound, and Arcanist provides Burn support as well as Inferno. Inquisitor also has great Burn support through Rune of Kalastor and Flames of Ignaffar, and -% Fire Resistance with Aura of Censure. The legendary Warpfire can also be dual-wielded to convert Frostburn sources to Burn damage, making Nightblade as well as Arcanist potential classes for a Burn build if you have two of these weapons.
Skills with highest base (per second) Burn damage:
Transmuted Callidor’s Tempest - Inferno: 426/sec
Rune of Kalastor - Ignition: 193/sec
Hellhound – Infernal Breath: 155/sec
Cannister Bomb: 172/sec
Transmuted BWC: 118/sec
This DoT type has a lot of support from the Nightblade and Arcanist trees, as well as Inquisitor through the Rune of Hagarrad. Further, conversion mechanics can be used with Internal Trauma to create more Frostburn; Scourge Strike from the Scourge relic is a great way to do this because it has a 50% Physical to Cold conversion as well as a large (350+) % weapon damage component. This could make going into Soldier a possibility for a Frostburn build, since they have lots of flat IT from Deadly Momentum and Oleron’s Rage. I would recommend making sure you have at least Nightblade no matter what you choose for the -% Cold Resistance (although Inquisitor has -% Cold Resistance as well).
Skills with highest base (per second) Frostburn damage:
Frozen Core: 292/sec
Rune of Hagarrad - Chillsurge: 232/sec
Absolute Zero: 126/sec
Amarasta’s Blade Burst: 124/sec
This DoT type does not have as much support as the previous types and may need to rely a bit on conversion from IT. That being said, there are some decent sources in the Shaman mastery along with a source of IT conversion, while Demolitionist provides more Electrocute bonuses and -% Lightning Resistance. Inquisitor also has a good source with the Storm Box as well as -% Lightning Resistance. Arcanist has a single source, but you’d probably be better off as an Elementalist or a Warder. However, the Spark of Ultos, when dual-wielded, can allow you to convert Frostburn sources to Electrocute damage which can make Arcanist or even Nightblade a viable choice, provided you have two of these rare weapons.
Skills with highest base (per second) Electrocute damage:
Transmuted Grenado - Shattering Blast: 172/sec
Wind Devil: 165-201/sec
Storm Box of Elgoloth - Lightning Tether: 145/sec
Storm Touched: 80-142/sec (Flat)
This DoT type is probably both the easiest to build around as well as the strongest. Witch Hunter is the obvious best choice, since both Occultist and Nightblade are the only two masteries that deal in Poison. Both have great Poison sources and damage boosts, and both have great -% Acid Resistance. Necromancer has some support of this damage type as well through Ravenous Earth. The devotions and gear support are arguably the best out of the DoT types as well; relics and components provide some of the best Poison sources to make up for the lack of many strong ones in the mastery trees. Because of this, you can probably make any class combo work with this DoT type as long as one of the classes is either Occultist or Nightblade.
Skills with highest base (per second) Poison damage:
Transmuted Dreeg’s Evil Eye with Blood Burst: 320/sec
Nidalla’s Justifiable Ends: 230/sec
Blight Fiend - Rotting Fumes: 169/sec
Blight Fiend - Blight Burst: 125/sec
Ravenous Earth: 125/sec
So now that the expansion hit, this DoT type is supported almost exclusively by Necromancer. However, with Decree of Malmouth, you can convert Burn, Frostburn, AND Electrocute to Vitality Decay, meaning you can get some serious numbers if you want to pick a second class that has lots of these sources. Apostate would probably be the best combo, as the Decree of Malmouth is for Apostates, Inquisitors have lots of sources of Elemental DoT damage, and a certain item even grants -% Vitality Resistance to Word of Pain. Shaman would also be a good choice, as they have strong Electrocute DoTs to convert and have good -% Vitality Resistance with Devouring Swarm.
Skills with highest base (per second) Vitality Decay damage:
Reap Spirit: 265/sec
Necrotic Edge: 137/sec
Blood Boil: 126/sec
Anyway, that’s about it! I hope this guide will help people in making new builds or refining old ones. Let me know what you think, or more importantly let me know if I’ve made any mistakes or left anything important out. I’ll be sure to add it in.
EDIT - Previously, the primer had listed that Aether and Chaos had corresponding DoT types that existed but were unlabeled. This has actually been proven false on page 3 of this thread; I went to consult my original source that had given me the previous information and found out that it was outdated. Aether/Chaos DoTs were a bug that was removed in v. 18.104.22.168 (source: Nine). Many thanks to DenisMashutikov for going out of his way to put up screenshots to prove that this was the case.
EDIT - I had previously mentioned that both main-hand and off-hand weapon damage counted as different sources. This has been proved false. Thanks to Cyrim and Coincident for confirming this.
EDIT - I had previously wondered whether multiple instances of a skill stacked with themselves (BWC, Wind Devil, Blade Spirit, etc.). I have confirmed this is NOT the case.
Thanks eisprinzessin =)