Paladin Healing Niche

I have a very hard time believing GC did Mimi and Hodir with 2 paladin healers and it worked just fine; possible and fine are not the same word. There are very, very few fights that require multiple main tank healers as well. Why would people bring multiple paladin healers to raid? And every other healer has the tools to be an MT healer, but paladins can't AE raid heal?

An apparent "double standard" exists because the game has far fewer healing specs than damage specs. Most 25-player raids are going to have a diversity of healers so it's okay in our minds for them to have more discrete niches. While there are many fights where single-target damage is not particularly useful, there are very, very few fights that are not tanked, and therefore where single-target healing is not particularly useful. Besides, while the paladin niche may be single-target healing, when I look at raid stats, nearly all of them are managing to heal people besides the MT. I've run 10-player raids with 2 paladin healers plenty of times. It works fine.
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