I'll never understand why a tank would use sprint in the first place in a dungeon after aggroing a mob. Just run with your team . . . problem (mostly) solved.

Anyway assuming you as the healer are geared properly and using heals over DPSing, if the tank still dies because he pulled a million mobs then the fault lies 100% with the tank. Grinding dungeons in this game shouldn't be stressful to anyone involved. If it is then you're doing it wrong haha.