Alright, I think I decided. I'm going to make a druid on the same account as the Shammy and Warlock on my new account.

When the Druid reaches level 26, I'll start dualboxing my shaman and warlock instead of the druid. The warlock will still act as a slave, and both Shaman and Druids level melee spec, so it shouldn't be too much different in that aspect.

I'm sure a squishy healer has its benefits, but I'd rather have a mail-wearing healer if possible. Theres more room for error.