This is the macro level answer. It’s impossible to balance classes to all ‘cap’ out at the same difficulty.
Unfortunately, community perception is a killer. Ion mentioned it at the last blizzcon, it’s almost like they need to overbuff a class to bring it up in the communities eyes and THEN nerf it down. Which is kinda my guess right now as to why prot warriors are so ridiculously OP. They were OP at the start of Legion only to get nerfed into oblivion and become virtually the bottom tierd tank where they stayed for the remainder of Legion. They maintained the same perception coming into BfA.
But.look.at.them.now. Let them be hugely OP and popular for a few months through the MDI, then nerf their DPS. The result, a totally different community perception of warriors, former God’s with less dps. Imagine this opposed to being the unanimously agreed upon worst tank who received a few adjustments and IP off the GCD - they would still be considered garbage.
I can sympathize with you tho, I’ve been running with an Spriest lately doing 18 keys and have been hugely taken back by her dps output. From a utility perspective she doesn’t bring what a boomy would, but from a DPS perspective absolutely competitive to our rogue/DH.
Same applies to ret, I ret keys sometimes for fun and people are constantly blown away at how good ret is right now - a ret paladin will melt reaping mobbs and if the tank pulls around their wings, get ready to see some huge numbers.
However, community perception hasn’t caught up. And until it does, ret=garbage in most peoples eyes.