To be fair, it's been a while since we've had a dungeon I can recall that had an Esuna-cleansable debuff that was actually important to cleanse (as opposed to, like, 6 seconds of poison or paralysis), much less one that had that *and* a heal-to-full-to-cleanse Doom. (Albeit in separate boss fights.)
So healers may well not even read the tooltip on that debuff to notice it's why someone dies on their first run. I try to read tooltips of any unfamiliar debuff (especially if it has a Esuna marker!), but I know that's a lot harder for controller players.
It's not really an excuse, mind you. But it is at least an explanation.