I use a G510 keyboard, so I have 39 abilities hotkeyed (and that does not include movement keys or mounts). I don't use the mouse to click anything really.
I play the following characters: Prot Paladin, Fury Warrior, Feral Druid, Holy/Shadow Priest, MM Hunter and MW Monk. Of all of those, only the Prot Paladin has empty hotkeys left over. It's so distracting to see that empty space that I placed the TellMeWhen buttons in place of those missing hotkeys, hah!
Anyway, Prot Paladin for me. Everything else is pretty bloated, though with this keyboard and my muscle memory super powers, I actually enjoy more buttons.