
Originally Posted by
Cenerae
I raided WoW at mythic difficulty until the first big content patch hit Legion (by which point I'd had enough).
The healing design there is that healers are intended to be throwing out heals most of the time. If you don't outgear the content by a fair margin, you aren't going to have much free time to actually throw out any damage. And WoW healer damage is also pathetic by comparison to what the DPS and tanks can do. The one exception was discipline priest, which was designed around healing through casting offensive spells, and even they didn't have amazing DPS (if you had solid uninterrupted DPS and never had to stop to do healing, you could match a tank or a bad DPS of your own gear level).
That doesn't mean that healers in high end content don't still throw out damage. In fact, it's a very good idea to since all WoW healers have at least one mana-free method of dealing damage. And that damage can be important when pushing through new content. But in a 20 man raid, your 3-5 healers are going to account for maybe 1% of the raid's total DPS. A little more if you have a discipline priest (unless their design was radically changed since I last played), but overall not a significant amount.
And as for dungeon content, if you're doing mythic plus dungeons, you are going to be far too occupied trying to keep the group alive to have much of a DPS window.
Compare that all to here, where the healing comes in periodic bursts, and where in between those bursts you generally don't have a lot to do because your healing relative to a WoW healer is much more potent, and where a simple regen can do most of the work to negate a boss autoattacking the tank. That leaves you with time where you're not doing anything. If you're not doing anything, then there's no reason not to throw out some damage spells unless you know for sure that you risk running out of mana later into a fight if you throw one more nuke out. Healer DPS is very strong and can make up a significant portion of a group's overall damage when played well.
That's why it's made out to be an expectation here, and why in WoW people rarely care about it. The way the tanks and healers are modelled are very differently. In WoW, healers are intended to do little else besides heal, since tanks take a constant beating and healers can't just spike a tank from near death to a comfortable health level with 1 OGCD.