I'm running a Druid/Warrior team right now, and I don't use any addons or key cloners. I do use Healbot when it's working, but that hasn't been for a while. It's not hard for me to remember the bindings of two classes (which includes 1-6, F1-F6, alt+1-alt+6 for both toons). Druid is easy to remember, as I'm just spamming 2 and 3, and occasionally rebuffing with shift+1 and shift+2.

I imagine it might be the same when using multiple of the same class. Just keep all their bindings the same.