I used divine aura on my cleric, but started taking damage again while the buff icon still showed 6 seconds left.
What kind of damage? Where were you? In RoS and beyond, the developers thought that the mobs should be able to get around DA because, paraphrasing, mobs would have learned to get around that by now. So there are a number of things that ignore DA. Ever try to pull a sabertooth in OT with DA on? Meanwhile I'm still having my Gate spell collapse and Evac leaving folks. I guess I don't have enough heroic int.