It's not harassment asking a healer to contribute a bit to the group when damage is at an all time minimum.
Heck for some healers dpsing actually mitigates dmg, Shadow Flare slows down enemy attack speed and Holy stuns.

SE wouldn't give you DPS spells if they didn't want you to dps. WHM got Aero III, Stone III, Assize. SCH got Broil and an upgraded bane. It's not mandatory, but you should utilize these spells when you can.

Personally, I don't see the fun in jumping around in a dungeon spamming emotes or chatting to your friends when you could be helping. If you have enough time for that, you have enough time to throw some DPS around.