I don't lead from the healer, but I do run a full melee group. The most effective movement strategy with them is using strafe. Leaving the tank in one place and spamming heals may work sometimes, but it's also a good way to wipe your group...like the one you mention, Karsh Steelbender. You need to melt the armor in the lava; you also need to get him out of the lava so he doesn't AOE your group to death.

I always prefer to lead with the tank. It makes it easier to micro-manage things like targeting/using things, taunting ads and positioning.