The ranged/melee DPS and healer ratings seem to be pretty consistent between anyone rating them.
But god damn if the tank ratings aren't ALL over the place. Paladin is consistently getting mid tier but I've seen monk and druid at both the top and bottom of the list along with the same for DK and Warrior. Demon Hunter is also either mid tier by most peoples' reckoning.
There's a distinction though - M+ or raids.
For raid tanking, Monks will always (unless destroyed via class fantasies and tablets) be the best physical damage mitigation in the game. Not because they take less damage, but because it is the smoothest and least spiky. We did some real silly shit, especially around the NH raid tier and still do silly shit now. I have to force myself to die on Argus, for instance, or else we get fucked as a raid. This will just propagate into BfA because our kit is extremely strong.
Similar to Monks, Bears will always be near the top for similar reasons. They have massive HP pools, decent cooldowns, decent (albeit nerfed) raid utility, and in general are one of the safest tanks to play.
The other 4 tanks are where the real questions are. I think if you're talking M+ you'd be hard-pressed to find a tank better than VDH. DK is probably right there with them. Prot pally has always been mid-low tier, and it doesn't look like it's really going to change. Prot Warriors it really depends. They got dumpstered pretty hard early Legion and never really recovered. Monk's only real claim to fame for M+ was we could kite really well.
All that said, I think the actual balance between the 6 tanks is closer than ever. Another thing to keep in mind is the person reviewing them - someone like Sco plays Warrior and Druid pretty exclusively, so he's hyper critical and knowledgable of those classes. He plays the other classes a lot less and may not be an ideal player on those.
