In that case you have a choice : make someone use up 1 of their role slots for a tank-healing spec that works and can stack, or make them take a tank healing spec that can't stack.
"Oh **** guys, we're at sicaron now; better call it a night cuz timmy and jimmy both brought warden."
I think you are indeed reading too much into what he said. In a raiding situation there are healing mechanics that are far more powerful than SS if stacked. In pvp they just never get used cuz of healing pushback and the high likelyhood that the spell will get interrupted.And, like I said... it kinda seems like Daglar felt this ability was overpowered in PvE as well. Or maybe I'm reading too much into what he said, but y'know. They have made PVP-Only changes before.