So, I started the game, got out of the room, found an axe and killed all enemies I saw. Then I tried to go to the next location, but couldn't break the door. And while the icons and the UI look really good and professionally made, other parts of the game(the combat, enemy AI, etc.) are very early in development or completely absent, so my biggest suggestion would be to focus on those parts first, and then work on the icons and skill trees. Also, if I was gonna do an RPG with multiclassing, I'd probably have one big tree for all classes instead of multiple separate ones, with every class being represented by one major branch, and sometimes the branches could connect, so that if you had a skill that's thematically similar to multiple classes, it could be obtained from all of their branches.
Other than that I found that having to hold RMB to rotate the camera was strange.
Oh, and I also found a bug:
When you try to equip a skill, and you start dragging it, it will sometimes "detach" from the mouse and drop somewhere in the middle of the screen, and there's no way to start dragging it again or to reset it.