Well that sounds like a not bad idea on paper. But well, it would bring more harm than good when implemented badly.
First of all, issues you mentioned of course can be a problem for ones but benefit for others.
Like for example tank deficit issue, this one is beneficial for tanks, because they get instant queues, people are nicer toward tanks, this one is especially beneficial for people starting tanking and trying to learn to tank because people wont just go instakick for every minor mistake, some will try to give some tips etc. Of course there are clinically stupid people who also have too big ego to listen to anyone but well. we dont live in perfect world.
Imagine AI tanks get introduced in way that they instafill every slot in each df group, less people will ever try to tank because unironically deficit of tanks can also encourage someone to try tanking, but when we have tank abundance in dungeons then less people will tank which means there will be less tanks for raids, and speaking of new tanks, most likely every new tank will be votekicked by every minor mistakes just to be replaced with AI tank. More fair option would be if AI tank will be added to groups that are stuck in queue for long enough time like 15 mins or 30 mins.
Second, adding AI NPC's to the world unironically wont help, people who want to farm are happy with fact that they wont have any competition, but imagine you add automated bots that just walk around and pick up every herb, rock or quest item. It will piss people off and will also cause inflation as AI bots picking up resources make them harder to farm therefore more expensive.