As a group we need to communicate and not let the burden of teamwork be put on one player. Should the tank discuss if he or she wants to pull a big group? YES! But as a healer, you too can tell the tank if they should pull big or not. We gamers are not mind readers, if someone wants to do something or you expect something from others, then tell them this.

When I tank, I take one of these 3 routes.
Route A: I ask partymembers if they are oke with me pulling a big group, depending on their answer, I adapt.
Route B: Nobody is saying anything, so I check the classes + gear and act according to this. If I have AoE classes in my group and the healer has good gear, I will pull a big group. If I am not reading any complains about the big pulls, I will continue pulling big groups.
Route C: I pull a big group and notice that the healer is not dpsing and sitting on large manapool. When I see this, I pull only big groups. If the healer is dpsing, I will support him, by pulling a small pack, so they can dps aswell.

Gamers during a instance expect too much, we should communicate more.