How are you boxxing healers?
With my healers, I've got ISBoxer set up to pass my num-pad keys only to those two accounts. When I hit num-pad 1, this casts a single-target heal on both the warden and the mystic. Num-pad 2 casts group heals on both characters (it might be a group ward on the mystic). Num-pad 3 casts the big single-target HOT and ward. 4 is in-battle rez, 5 is death-prevention, etc.

I don't just heal with my healers. They also melee and cast damage spells. When I need a heal I use the num-pad, which only passes through to the healer accounts, so the other DPS classes just keep doing their thing. It's worked fairly well and was easy to get used to.