As far as my pally goes..

My one button covers almost everything.
The only thing I really do without it, is start Divine Plea.

Granted I do have emergency buttons like Divine Sacrifice, Hand of Protection, Single Taunt, AoE taunt, but if the pally pulls, the other toons have never managed to take threat, so I've not needed any of these. I do use taunt, to take aggro if I pull something at range with 4x shammy nuke.

If I put Divine Plea, into my master click macro, which calls my 96969 macro (purely for space reasons), and manually ran my pally into groups.. ie, paladin is getting initial threat, my one-button would be fine.



Cannot say the same for my Druid.
Have never had a Warrior beyond 40th, but they were a lot more things to click.
And a DK would likely need to most clickable buttons.