Yes /10char9 out of 10 tanks that I come across in M+ seem to be blind and illiterate, because I've got a WeakAura that automatically sends a message to the party when I drop below 30% mana, and even with that, tanks ignore it and continue to go off chainpulling when I'm at 10% and drinking. And with how close together most trash packs are, I have barely any time to drink. I end up spending the entire dungeon below 40% mana because tanks just chainpull nonstop.
No, I can't "drink while the tank pulls" because they often just start taking loads of damage as soon as they engage mobs. Even trying to drink after every pull, I'm running up and just barely saving the tank from death as I struggle to spam heal them, which wastes even more mana.
Should I just let them die if they won't let me drink? That's likely the only way I'm gonna get their attention if multiple party chat messages aren't doing anything.