I’m no expert as I’m still in the process of getting all of my characters (like 24 of 'em) to Elite before I start pushing that difficulty in earnest (it’s just the way I play), but I’ve made an Aether/Vit Spellbinder that uses both AAR and DE (I just wanted to make a full channeler build) and to me, they are two very different skills, and each fulfill a different role. Though, take what I say with a grain of salt, as I’ve not played that character much since the addition of piercing to AAR (and the associated damage nerf).
To me, DE is a clearing skill. Depending on the environment you fight in, enemies won’t always line up for you to be melted by AAR. But you can be almost certain that enemies will do their utmost to close in and surround you (plus, many just spawn right on top of you), which is where DE excells. Where AAR will be killing monsters one at a time (bar the occasional ranged monster caught in the line), DE fulfills the AoE duties at close range perfectly. DE also has a fairly significant DoT component which AAR lacks (unless you scale Electrocute), and due to the random nature of the “AoE scatter” DE has, the skill’s DoT will affect many more monster than its max target cap would suggest. Seeing as the DoT is fairly significant, a single lash of DE can apply enough DoT to just kill a trash mob outright. So with a brief channel, you can easily down 10 monsters with DoT in the next few seconds. AAR then fulfills the DPS function when more resilient monsters like bosses come around. The two skills can also function fairly decently when comboed together for this reason, as you can just quickly apply the DoT from DE and then channel the rest down with AAR to enhance your DPS.
Another important aspect is sustainability, accessibility and survivability. It takes a hot minute for a new character to get to AAR. It takes a bloody eternity for AAR to become sustainable for a new character. At lvl 75, I still can’t keep AAR going too long before I run out of Energy, despite a hefty amount of regen. Using AAR as a clearing skill at that point simply isn’t suistainable, while DE not only provides better AoE but isn’t as much of a resource hog either. In addition, both skills require you to stand still in order to get your DPS out, and both incentivise the use of caster gear. That means you won’t be particularly tanky (low armor, no block and shield synergies, etc.) and will make for an easy target for ground-target abilities. AAR had my health getting dangerously low if I channelled a little too long in one place, where DE allowed me to just stand there and tank it all up front without a worry due to its built-in lifesteal and offensive ability debuff. Overall, it just makes for a much better facetank clearing skill than AAR.
Obviously, I imagine that if you were to make an AAR-only or a DE-only build, the comparison would probably look very different and there, DE might really lag behind in terms of damage. But when put next to each other, they really seem to me to fulfill different functions and excell at different things, so much so that I put them both in the same build and it didn’t feel redundant. It is possible that once my character is fully equipped with lategame sets and gear, I might just have to choose one over the other, as I won’t be able to properly support both, but I’d wager that DE will still make for a better clearing skill through sustainability, convenience and fire-and-forget capability than a fully supported AAR would.
Sure you can get around, but it slow as hell in comparison.
