Yes, I'd considered that, as I mentioned, though their post reads more the other way. Anyhow, the healer was quite aware they weren't/barely dpsing I'm sure, and the tank doing small pulls implies a lack of dps, therefore it isn't a stretch to say the healer could easily take that as a dig at their expense - it's taking longer because
they aren't dpsing, rather than the actual dps classes not doing what they need to do. I thought that was obvious myself, but apparently not.
While a healer contributing dps certainly helps, them not dpsing has
much less of an impact on the length of time a dungeon takes than if a dps just single targets everything and doesn't even do proper combos.