My comment regarding tanks turning bosses applies only to bosses, I've witnessed numerous occasions where the tanks re positioned the boss to face away from me without having to hit the engaged key, after that the dps AI sort themselves out. On normal enemies yes, they run around if they lose a bit of aggro and don't reface them. However on normal mobs to stop the dps getting aggro I've found you need to hit engaged every time an enemy dies or the AI will just attack whatever is left standing randomly. On bosses however you don't want to micro manage them at all.
It may be as you say with the AoE, the AI re-positioning and a little luck has meant that they have stayed clear of these, still that would be extraordinary luck considering the number of times my THM stopped casting to move out of the circular AoE the SV boss uses randomly on ranged players. Still it could be as simple as when foe does xyz, move - which is not a true dodge as it means they may or may not managed to avoid the skill and that they move even when they are not the chosen target. This possibility is not one I had considered but in terms of simplicity it would allow AI to avoid some AoE while their general toughness would mean if they do get hit its not too much of an issue. Still their toughness does not account for everything - I had a lancer that got caught in Rime Breath and that was ouch but the healer had no issue patching him up.
