RNG for loot is crap. I get to level 20 and just get bored with Threatening because I can't advance to Perilous because I keep getting the same very small selection of poor items.
Many skills are just downright useless compared to others, and are made more so by being unfairly restricted to 4 abilities on the hotbar, while some classes have at much as 12 possible. Such as the parry abilities - they are difficult to use and are harmful when used against boss or even just high end enemies because they just blast through it and own you even if it is properly timed. Other enemies ignore the ability entirely, like the wraith's melee attack which hurt you without even triggering it.
Demon Commander is terrible. His teleport does too much damage for how hard it is to avoid. I've been running full speed on my Katari during a charge and have been hit by it when I was the intended target. Sometimes it's literally impossible to avoid and it either 1 or 2 shots you.
Enemy archers do way too much damage.
Templar Commander has way too many instances where he can't be hit by anything. His death animation is completely screwed up and while he is technically dead he still shows as having health and persists for too long. Newer players waste so much time trying to damage him during these animations. He can also stun lock you to death with his earthquake attack, and being stun locked is not fun.
And urns are a tedious way to get money. But every 2 or so urns is about the equivalent of getting another money chest. Even if they weren't buggy I still don't like them. I've ran into many players who ignore them and are just obsessed with outscoring you and running ahead that you either spend most of the match gathering money and playing catch up and not fighting, or ignoring it and have everyone lose out on money.
There are many various glitches that need fixed, like the urns not breaking properly, skills not triggering or breaking, Fear Demons ending up in inaccessible map areas..
And please remove the "are you sure" from buying chests with gold. YES I AM SURE THERE IS JUST 1 BUTTON! Shut up and take my money!