Bardam's Mettle is one of those dungeons where the adds hit like trucks, so I'm not surprised to hear you're struggling through that place. I'll also add that I've seen more than the one tank intentionally eat telegraphs in there, so that could also play a part. Anything else I wanted to add, Cynfael already covered. Tanks using cooldowns, DPS AoEing, tank pulling according to the AoE DPS capability of the party... those are all things you as a healer have little control over, but that heavily affect the survivability of the party.