Most healers in DF don't DPS, and it doesn't take more time than when I play my Holy spam WHM and get mediocre DPS ( which are legion). That's the reason why I mostly play BLM in dungeons now. Healers DPS is low, way too low to compensate for terrible DPS.

Back to the topic, there are a lot of tanks these days that don't pull wall to wall. More than during 5.0. I wonder why. It's a bit of a waste of course but I don't blame them if they aren't comfortable with the content.