Which damage sources are blocked by shields?

Grim Dawn Gameplay Discussion
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Question 1: Which damage sources are blocked?
The Game Guide states that “when you are struck by an attack with a shield equipped, you will have a chance to block some of the damage (shields can block any damage type).”

However, it is not entirely clear to me which damage sources are blocked by shields. The ‘it can block any damage type’ part can refer to the kind of damage (e.g., elemental, chaos) and not necessarily mean that all sources are blockable. For example, can you block all spells? DoTs (and if so, per tick or per application)? Ground effects? Life reduction? Reflect?

Question 2: Can all blocked damage sources trigger ‘on block’?
Second, just to be sure: can all damage sources which can be blocked also trigger ‘on block’ effects? This seems like an obvious ‘yes’, but Grim Dawn isn’t always consistent. I’m especially interested in how this interacts with DoTs: can a DoT only trigger ‘on block’ effects once in total, or per tick?

Question 3: How exactly does blocking reduce incoming damage?
Thirdly, as one of the few cases of absolute damage reduction, it matters a lot how blocking lowers damage. For example: if can block 100 damage, and a single attack does 80 damage + 80 over 4 ticks, does it block 100 out of 160 damage, or does it fully block every individual damage instance?
This makes a massive difference (especially when you’ve got -100% block recovery time).

I sadly do not know how to uncover such mechanisms from digging into the game files, so I would really appreciate clarification on these questions!

On a side note, because blocking reduces damage before armor does (which also reduces damage by flat amounts), it seems to dramatically reduce the amount of physical damage you receive, which is fascinating.

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Shields won’t block AoE afaik or Dots.

For anything else it blocks as much as it states in the third menu tab. If it says 3K That is how much you block on each hit.

Recovery reduction is great. I recommend either ~60% or full 100% if you wanna go there. Anything in beween is a waste. The difference between 90% and 100% is huge. But 60%-90%…not so much.

Imho at 60% i’d focus more on block chance, a pretty hard to get stat. 80% is almost God like although i generally stop at ~65%.

Also increases your %chance to block procs.

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Can’t block any of this except the few spells that don’t have an area of effect or damage over time.

As you have already found out, blocking is most effective versus physical damage where your resist is typically low. Against other damage types resists take care of the vast majority of damage and you won’t notice the effect of a shield as much, although it’s of course still there.