I just want to clarify further why I believe healer should be allowed to pull more if they want because I believe those tank's are basing their pull entitlement reasoning on selfish desires which is imo no defensible position in content that relies on teamwork.
How I see it, healer is the one that will have to deal with any problems or excessive damage. When the situation isn't clear, the tank will ask the HEALER if they can handle a bigger pull, not the other way around. A healer won't ask a tank if they can handle a bigger pull because the healer will know based on how much damage they are taking and how much they are capable of healing. What healer does usually is ask the tank to pull more, not ask them if they can handle it because tank doesn't get to decide that.
Responsibility to keep everyone alive in the end is the healer's, so they are imo the only role that may complain about the size of a pull, the others are constantly at mercy of Healer keeping them alive basically. This is why it makes completely no sense to me why you'd get upset at a healer if they decide to pull more. Considering this there's really no good reason why it would not be okay for a healer to see the situation and decide that prepulling for tank will lead to most efficiency. The only arguments I can see for tank to be against this is 1. they won't be as comfortable 2. it breaks their immersion 3 it hurts their ego.
All 3 of these reasons are entirely selfish and don't consider the group's best interest. Meanwhile the healer's decision to prepull increases efficiency and makes the instance progress faster, which is in the whole group's best interest and is the purpose of forming a group with the 3 distinctive roles in the first place.
If the healer prepulling did lead to a wipe, then the healer failed their job and they will take the responsibility for it, only then you may complain imo and perhaps kick them. Before that it's none of your business to determine what's okay in a matter that increases efficiency and doesn't result in deaths.
Just as a sidenote, I'm not speaking out of bias. Healer is most likely my least played role and I'm pretty sure Tank is my most played role for dungeons. I've never mained a Healer for long, almost always Tank or DPS. Right now maining Tank.