Most NPC's where the NPC is not the "duty failed" objective don't dodge AOE's. Look at any FATE that involves NPC's.

The Job-specific NPC's may or may not avoid AOE's. The problem is that in most solo instances, the guy you're supposed to protect/heal already has enough HP to just sponge damage (exception most of the WHM's job quests, where you're supposed to heal certain characters. In the case of the level 70 one, you may end up throwing everything including benediction on the NPC while you take out voidsent.) What you're instead supposed to do is collect the hate of anything with an AOE to avoid the NPC's taking the damage.

More or less, the game's AI needs an improvement, for both AI-controlled friendlies and AI-controlled enemies to actually try to dodge AOE's.

Other games, incidentally have done such things and typically the result is that melee characters simply take the damage instead of trying to dodge it. If you make the AI too reactive, it will react faster than the player. Thus you get the unbeatable monster. Which incidentally, that is how the "ledgendary monster", "field boss", and such type of monsters originated in Ultima Online. Because the monsters in that game ALSO leveled up by defeating players, that's where players first decided to band together to take down Ultra-powerful monsters.

So to have AI players with "human" like reaction times requires making them react after 1.5 seconds to AOE's, often not enough time to dodge an AOE since the cast time is 2.5 seconds for most skills.