Shock horror. People don't respond well to lazy players looking to skimp by content by having them do all the work. Hate to break it to you, but if I have 300 casts in a fight and you have 100. I've done three times the work and may be a little salty about it.
It's an example of how necessitating healer DPS in any content wouldn't be good design. It leaves no wiggle room. That doesn't mean healers should get to be lazy because dungeons are easy.
