"Small" ingame statics, like columns, fires, etc. obstruct certain skills with inbuilt pathing, like Whirlwind, from acting properly. Once a character bumps into them, he often stops, which presents a tactical deficiency. It would be nice, if that issue were fixed.
There're several non-used half, or almost-working server-side skill functions present, including a half-circle area effect melee strike. If those were "refined" and used for character, or monster skills, that would improve the game experience, IMHO.
I believe it's been suggested already, but having an extra UI slot for stances(auras) would surely be beneficial. Right now, the characters using stances are robbed of properly utilizing right mouse click normal attacks. Not to mention the right mouse click skill micromanagement only possible because of aura working for a time, after being switched off.