It's a tanks job to ensure that their healers and DPS can keep up with the pace they set. If they don't even do that much, they're the ones that suck, not the healers. I think a lot of tanks seem to forget that not every one can do the DPS needed to kill huge crowds of enemies quickly, and not all healers have the heal strength or MP to keep them topped up through it. They just assume everyone is overgeared and pull accordingly.

For me, I'll always assess the situation first. I'll ask before pulling bosses to ensure the mechanics are known and avoid pulling more enemies than my team can keep up with. It doesn't matter if it's my 4th or 100th run that day. After all, if the team wipes you'll only spend even longer in the party than if you just do things at a better pace.