Well in that case...
Feral is the easiest to play, because you have no worries about roots. You can shift out of most of them, and are immune to polymorph and hex. A DK has to use his skills effectively to get decent mobility. Additionally, cooldown stacking works good for Feral, so if all you want is to cap, just pop all cooldowns and try to burst someone.
If you don't care about a high rating, and just want to cap, the keybindings matter nothing. If you want to get a high rating in arena however, you absolutely need most of your skills keybinded properly. Once you get to decent ratings (2200+), you'll understand. Until then, I can understand it feels stupid. You just don't know how important it is on decent ratings until you get a decent rating yourself though.