
While I'm not one to QQ at healers for not DPSing in most content, I can't seem to wrap my head around the "why" of it. Like... if I played a WHM or a SCH and just sat there healing all day (or throwing a HoT/heal in my tank's direction when he gets below ~90% HP), I'd want to blow my head off. It's like if I chose to play a DRG and decided "You know what? Positionals aren't really my thing." Can I do it? Sure. Can I get away with it? Probably. But how can you tolerate it? FFXIV is already -- imo -- a pretty stale game most of the time, so why make it even worse?
...But I mean, to each their own, I suppose. And the argument of "No matter what I do, I'll get chewed out for the opposite!" is moot, since you're not being chewed out for not healing or not DPSing, you're getting chewed out for not doing both proficiently. A good healer -- as some have already stated -- can do both harmoniously and without sacrificing the other.
This is a little off-topic, but really, all it takes if you aren't comfortable with your ability to do something (utilizing cleric stance in this case) is a quick, civil "Sorry if I don't hop into Cleric too much, guys. I haven't wrapped my head around it enough to be confident flipping it on and off in this content" at the beginning of the dungeon.
tl;dr for the second bit: Just own up to the fact that maybe you're just not at a point where you can comfortably use cleric stance (or any toggle skill; deliverance comes to mind for WARs). We're not all perfect right off the bat, and barring Savage content, I don't think anyone's expecting perfection from you.