The only problem for me with keys has been players from Quelthalas, Azralon and Ragnaros. If you get anyone from those servers you’re either gonna be baby sitting someone who stands in all the mechanics or you’re gonna have someone who is basically AFK the entire key, without exception.
Maybe 1 out of 5 of those types of groups I run with are good and even then they can barely do mechanics and DPS at the same time. I think people from those countries are just all on potato machines with potato internet and potato everything.