First of all, I am well aware this is early alpha and following is my thought on the current state. I am sure it will all get better though and I really enjoy the game and look forward to its future development!
1) The default controls are very unintuitive and clumsy. I dont understand why primary attack is binded to same key as moving.
2) The optimalization is really bad (early alpha, I know) With 2gb graphic cards I am seeing like 10-20 FPS on lowest settings... I am sure this will improve though!
3) The huge ammount of enemies and combat as it is doesnt fit the ''lore''... I mean sure inquisitors are badasses but I dont believe that single inquisitor could kill one, not to say half a dozen of Chaos Space Marines in hand-to-hand combat. I believe that more lore friendly and gameplay wise enjoyable would be to have MUCH fewer enemies but with higher HP to acutaly make the combat less Diablo-ish and more tactical and rewarding. I really dont enjoy killing hordes of enemies with single blows. I really hope this is as it is just for the sake of testing and will be changed upon release.