Explain why Dru hp was fine but not pally hp?

Q u o t e:
Well, there's where you're wrong. Survivability isn't synonymous with EH. And tank survival has become much less about being able to survive "worst case scenario" damage, and much more about correct usage of cooldowns and healer performance. You can't survive a healer disconnect on Festergut 10 man, for example, no matter which tank you play. And avoidance and cooldowns matter a lot.

Q u o t e:
EH matters, but it's a simplification that doesn't tell the whole story. EH doesn't explain why warriors take less damage than other classes on Saurfang. Or why Druids were the best tank for Anub'arak. Or why DKs work great as tanks for Keleseth.

Q u o t e:
Blizzard doesn't agree with you. They think that balance is tanks completing content.

Quoting all three of Zarko's lines here. Because I like them.

One caution is you have to be really careful in how you factor in cooldowns to estimates or simulations of tank survivability. Some attempts just assume that e.g. Barkskin is responsible for X% of damage not done over the course of the encounter. That might be true on some encounters, but it definitely is not on others. When you can or need to use those abilities makes a big difference. On some fights, those cooldowns just give you a little slop room if the healers have a lot on their plate or have to move or something. On others you just aren't going to survive without a cooldown.