What I mean by CLEAN and TIDY is the class thats abilities all make sense, there isn't any abilities that are useless and every single ability the class has makes perfect sense just by looking at the ability.
For me I'd say Frost Mage by far is the most tidy class in terms of all of the abilities the class has, everything just fits and makes sense. Deathknight abilities for example...just seem to be all over the place, 1/3rd or 1/4th IMO of DK abilities just seem like a waste of space and need to be mutated into other abilities or removed all-together.
For me atm, every key-bind I have on my mage seems to make 100% sense, where as on my other classes, the keybinds I use just don't seem like they flow anywhere near as well. Maybe it's the way the Mage class is played? I'm not too sure.
This is why I think mage is so clean and tidy...it's such a basic work up of a class.
ATTACK: icelance,frostbolt,frostfirebolt
CROWD CONTROL: deepfreeze,cone of cold,frost nova, pet nova,sheep,counterspell,ring of frost
DEFENCE: decurse,mageward,icebarrier,manashield,blink,slowfall (for dispell protection)
Very basic compared to other classes IMO, I think rogues might be as tidy as this maybe.