Holy crap the new AI.

[Mrbloodworth]

I was wondering why some mobs were running up to me, and then making gestures at me (but not attacking). Apparently mobs now have their own buffs, some of witch require you to attack them first, sneaky bastards!

 I also noticed that mobs now avoid you, and will attempt to some times get beside or behind you, for positional attacks, they will also move from tree to tree as they approach, breaking line of sight (im a hunter!!). There also seems to be more buffs than this (Noted by the new green red ETC.. Circles around the feet). I do not fully have a grasp on the whole of the changes, but it has made even trash mobs way more interesting. Some creatures even spawn, choose a buff, then act accordingly, like a modular AI.

Fantastic so far.

[Tarami]

Yuppers, every sentient mob in Moria got three stances to choose from; aggressive, defensive and inspirational. First two are self-evident and inspirational stance is a buff stance where they use AoE buffs and heals on their allies.

There's a neat little thing about the passive Grodbyg larva in the same vein. At first, they got the "Tough carapace" buff which gives +50% defense, but if you stun them in some way, it'll become "Cracked shell" and instead increase damage taken by 25%, while reflecting 25% of taken damage back to you as Acid damage. Messy business killing larva, I suppose.

Oh, and Grodbyg Queens infest you á la Alien. If you don't cure the disease before it expires, it'll summon another bug.

[Cheddar]

In addition some skills have new uses.  The Champions yell ability (a taunt) will cause some of those tactical mobs to lose it and run straight for you.  Turbine has redeemed themselves with this expansion!

[Mrbloodworth]

Honesty, those that talk about a more dynamic AI, should check this out. Its not H.a.l-2k, but its much more advanced than most mmos. You may have had to have played before this change to see the real difference.

[Soln]

given the mobs often break combat and run behind or beside you, and/or just leave your front view so you CAN'T hit them, yeah it's a lot more complex than most.  Keeps you on toes for sure.