Enh can boil down to 3 buttons. 1 for totem, 1 for LB/CL, 1 /castsequence macro for everything else.
I mean if you don't care about dps you can play any class with a button.
Holy pally denounce spam! Not sure how good it is, I am sure it is awesome while low level.
Why is there no "Demonhunter" hero class yet? He was only the coolest hero in WC3. Get busy Blizzard.
The class with the least required rotational spells to fully manage their rotation is probably Combat Rogue.
1) Keep Slice and Dice up
2) Keep Revealing Strike up
3) Use Eviscerate at 5 CPs
4) Sinister Strike
Fire mages as well if you only count single target rotation:
3) Inferno Blast
1) Diseases - Outbreak/Unholy Blight/Plague Strike
3) Howling Blast
4) Frost Strike
1) Colossus Smash
2) Mortal Strike
With 5.2, the Unholy rotation is going to get close:
1) Put up diseases with Plague Strike
2) Festering Strike
3) Dark Transformation
4) Scourge Strike
5) Death Coil