Couple things
 

Bug's I've noticed are when fighting sometimes I am Ally to the mob and cannot attack. Also THe Stun bug I have ran into where I am permastunned. Another thing is, it seems AC is not right I get hit for almost full damage all the time. I equipped and 24000 ac item and it seems normal with a large amount of ac.

Another bug I ran into is mobs assisting like I fight something in Qeynos the whole city aggros on me, same in Hate Plane.

Aggro, could be a database issue.
AC.. we've never had accurate avoidance/reduction.. that's just not going to happen without a lot of statistically analysis. Redoing attack and damage is on the table though.. it will never be 'perfect' to Eqlive.. ever.