It's a balance. I'm one of those tanks you discribe and I base my pulling on:
1) do I have cds?
2) do I think the mana will be enough to heal?
3) can I avoid a lot of damage by kiting?
4) do we have hybrids who offheal?
5) can we keep trash cc:ed?
I expect the healer to drink when s/he needs mana and I expect to have to deal with a lot of damage without healing for a bit. I can see how frustrating it can feel to never get 100% mana and "wasting" good ol' drinks.
The change to how mana return from drinks work in SL probably hasn't sunk in completely either. I'm talking about how the mana return from drinking ramps up the longer you drink, starting low instead of being the same amount per second like in BFA. Also fish feast was nerfed, right?
That said, if the healer communicates that they want full mana etc then I ofc listen and wait. (same goes with rogues flaming me for not letting them restealth, I'm sorry, ok?! I forget that
)
Edit:
I don't know how you get the tanks attention if they don't listen. If we die and I hear "I HAD NO MANA" from healer then I say that I misscalculated it and say I'm sorry. That means I listen though... those who don't? Whisper them maybe? No idea.