WAR dungeon healing is out of control as usual and PLD has always had clemency to pick up a bad run where the healer dies but GNB is not gonna be staying alive without healer any better than DRK is and for some reason nobody seems to have a problem with that.
Saying it's abyssal and then nothing is a bit dishonest since you're completely ignoring TBN which in a mob pull is effectively healing you for 25 % of your max health every 15 seconds. Hell, you can even use it on bosses; it's a hit on your DPS but so is clemency. I really wouldn't want to make the baseline for viability around the ability to carry people who don't know how to play the game though. I haven't had a single trouble with DRK wall to walling in EW dungeons, neither leveling nor expert, and as the graph above shows there's nothing particularly wrong with DRK dungeon heals. I will admit though that I haven't ran expert for a couple of weeks since I've had no reason to and I'd imagine a lot of good players have not been in that roulette for a while since there's nothing to gain from it until the patch tomorrow when I expect it'll get better than whatever is going on in there right now.

Hell, I think later I'm gonna ask the healers I know if they've noticed any tank other than WAR standing out in any way in EW dungeons and couple that with a question of if they've noticed any tank having a higher chance that who ever is piloting them is not mitigating properly or is otherwise playing badly.