Prot warrior main who mained it since TBC....
Warriors were freaking hard to kill in Legion too, and did awesome damage + could abuse spellreflect on a bunch of stuff (Medivh for example), but nobody gave a shit, because BDK's were so massively OP.
The biggest nuance of the class (one that still remains, but is less evident) is that a warrior played badly back then was completely useless, while played well they were very good. Granted in BFA if you're played badly, then you are a bit better off (anyone can use avatar and facesmash thunderclap for good damage) but if you don't know what you're doing, you will still die.
I think a lot of the perception of warriors as invincible is a result of the meta effetc- because of the damage, tonnes of *really* good players re-rolled warriors, meaning that a spec which requires good play to be decent has a much larger proportion of the best players playing it.
I honestly think they maybe over-nerfed BDK survivability, and the fact that the Reaping replaced Infested was a big impact on BDK's (no longer needing the grip as much).
VDH and Guardian still need a buff, but I would be careful with how much they are buffed - the defensive buffs they made to warriors had everyone pre-8.1 saying that warriors were still going to be trash, in part due to the fact that people thought the def buffs weren't enough, and in part because warriors bring (probably?) the least out of every tank in terms of group utility.
What nobody accounted for was the interaction of bastion of might, avatar, and reaping, meaning that we became able to drop absolutely nuclear AoE. The survival buffs seemed terrible, but somehow warrior is now invincible - there's no reason this won't happen with one of the other tanks this time round, with essences and the new seasonal affix.
My money is on Paladin being the new go-to tank, either that or back to BDK