Years ago I got myself in a lot of hot water fighting about healing in raids. At the time I was a retribution paladin in WOW and the fight was about whether or not I should reduce my damage dealt in order to provide healing to the raid. I was advocating for the use of Glyph of Divine Storm that randomly spewed healing onto the raid to the tune of about 3% of a healer's output, which required me to give up Glyph of Exorcism which increased my damage by about .5%. There was much disagreement and shouting and gnashing of teeth.
That debate has come again.
This time it isn't even close. I am totally right. But people don't seem to believe it, even still.
The details are the talent choice for Retribution paladins at level 75. One choice is a really piss poor attack that is basically only useful for levelling early on and solo world content. The other choice is a spell that is only good when you are being attacked in melee... so really only useful for levelling and solo world content. The third choice is Word of Glory, a very powerful heal that is comparable to big healing cooldowns like Tranquility or Healing Tide Totem.
And the professionals basically all say you can just take whatever because none of them are any good.
The thing is, Word of Glory requires that you give up damage to use it. You replace a usage of your best finishing move with a Word of Glory cast. To evaluate how good this is, I figured out over the course of a raid how much each ability would do. If I use Word of Glory as often as possible I will output about 18% of a healer's total output. Each usage is about half as powerful as a major healing cooldown, but I can use it a lot more often and I can use it twice in a row if I want.
Doing this costs me about 4.5% of my damage. That isn't nothing, but it means that I am actually outputting a serious amount of healing that can potentially change the course of the encounter. In the original debate years ago I was getting a better ROI - I got six times as much healing per dps (3% from .5%) whereas now it is only about four times as much healing per dps (18% from 4.5%). The big difference this time though is that the healing is controllable. Word of Glory has a 1 minute cooldown and can accumulate up to 2 charges so I don't just spew out healing randomly, I save it for when something terrible happens and then pump it out. This is basically the best kind of healing because I let the healers do their thing for most of the raid but when disaster happens or the one really awful ability hits I can step up and deliver a really serious amount of help.
This to me seems like a no brainer. You don't have to cast Word of Glory on any given boss if it isn't going to be helpful, so taking it has little cost. If healing is being solid, you can just keep on doing damage. However, the ability to pound out a really big chunk of healing on demand when the situation calls for it is extremely powerful and raids really ought to be taking advantage of it.
The fact that Holy paladins don't have a good big healing cooldown like this is a real factor, but people don't seem to have noticed that you can just get a Ret paladin to do that in many circumstances. If a healer didn't bother to talent for a great healing cooldown (especially when the alternative is pratically irrelevant) they would be pilloried, but apparently Ret paladins aren't expected to.
This all goes back to arguments about raid slots years ago. Hybrids like paladins were often brought on raids for their utility and they had lower damage to compensate. Eventually Blizzard decided that this was a poor design and they decided to give everyone comparable damage and utility instead. Getting there took a lot of crying from hybrid damage dealers, and there was a huge pushback against the idea that they should sacrifice damage for defence or buffs. I get that. It sucks to be a damage dealer and to see everyone else dominate you on the meters. It feels good to look at your numbers and see that you are keeping up. Some people can feel good about protecting and buffing, others not so much.
But this mindset of 'damage dealers should ignore healing' is not ideal for pushing the hardest content. At some point you absolutely have to figure out how to squeeze the absolute most out of your raiders and when you have the option to bring some really powerful stuff to the table at a cost of damage you have to consider it. Sometimes it is the wrong move, certainly, but other times you give up a single offensive cast to have someone in your raid live instead of die and then it is a massive win. People are just letting themselves get too locked into the idea that healers do healing and dps do damage instead of thinking that there is damage to be done and healing to be done and you just have to figure out the best way to cope with that.
Yes, it sucks to give up damage and lose your spot on the damage meter. Yes, noticing when the raid takes damage is annoying because you only want to focus on dps. But at some point you need to realize that you win when the boss is dead, not when you are on top of the meter, and this means that you absolutely need to use tools like Word of Glory. It isn't a small thing, it is really powerful, and ignoring it is a real waste.