I think maybe you and I have different definitions of healer stacking. Three is just about necessary, with two being "acceptable" in many but not all cases. Four you can say is knocking right on the door but isn't beyond control. Five or more I would consider stacking, as at that point you only have 1-3 spots for people who can actually bring any real damage or interrupting power. As you said, more healers brings better holding presence. As I said, however, there isn't a whole lot of capturing power, which is the other half of the main objective.

Regardless of how I feel towards the tactic (it being absolutely stupid and time-wasting), I'm not so sure it needs to be shut out altogether as there ARE ways to deal with it. Maybe I still feel bad about what happened with Cleric Stance and don't wanna see healers take another hit in any fashion.