If a tank does a big pull and causes a wipe, it's 100% the tank's fault, no question. There's no shared blame with the healer.
If the tank assumes, they get what they get. If they rage because of a wipe, they're bad, not the healer.
Many tanks assume the healer can handle a pull that brings everything in the dungeon, but that's just a baseless assumption. No reason to feel bad at all if it was too much for you.
If the tank was any good as a leader they could have asked or started out with smaller pulls to test you.