Please consider removing raid level accuracy requirements from dungeons.

[Rongway]

nothing else to do if nobody needs healing

That's the thing though. There is something to do. Cast offensive spells. So what if they're going to miss?

The accuracy requirements don't prevent you from casting spells or being useful. Any damage above 0dps is a gain. No matter how badly a healer might want to put out 2000 dps, that's not a healer's job, and the dungeons should not cater to healers so that they can do someone else's job. Put out whatever damage you can. Just don't expect the game to let you be a DD-who-heals instead of a healer-who-DDs. Don't trivialize the people who are actually there to kill things.