As nightshade said above me, do one dungeon post 50 and you've done them all, worse case you pull 2 groups and then you see.
And I don't understand how tanks feel like their job is difficult or pulling more is anything different than pulling one, let me describe both gameplay:
1 pack: Run to the pack -> press a CD or two and aoe -> keep a cd rolling
2 packs: Run to the pack -> aoe -> go to the next one -> press a CD and aoe -> keep defensive cd rolling.
And as unbelievable as it looks, 3 packs is the same! Nothing you do as a tank outside of pressing a cooldown actually affects anything.

Then yeah, your healers and dps must actually press buttons and learn what they do, elementary knowledge is hard, like prime numbers as we see in ridorana.

If you were seeing someone doing a 100M sprint by walking instead of running because "it's more comfortable", you'd wonder what kind of clown it is and that it's not for them. Here, we have the same case: the game is made for multipulls but you just do single target pull because you don't want to put any effort and then you complain when people say something about it with a "they are toxic".

You won't learn unless you actually do it, same for healers, and if you fail, it means you need to learn because you are not up to par and not cower and only go for single pull because "it's scary someone died in a videogame and we lost 60 sec", which is still less than doing single target pulls. You learnt million of things in your life, that's just another one, you don't have to put less effort in it because it's an "online game", that's just selfish for the others.