For a big pulls to work, all players must be on a same skill level and decently geared. That's not always a case in 71-79 leveling dungeons, and I'm having huge problem with players who takes these dungeons as some kind of speedrun competition.
1."It's sub-optimal play" - he says. How can you expect optimal play in a leveling dungeon, where players are learning their jobs and don't have optimal equipment?
2. Yes, it is acceptable and it MUST be acceptable and yes it goes two ways. If you insist on big pulls when tank or/and healer can't handle it, you're not doing any favors and you're just stressing everyone out as hell. You like pushing max effort? Ok, just bear trough leveling dungeons until lv80, gear up and go to savage or ex raids. This is where you can demand everyone to play perfectly and up to max standards. But please don't expect it in leveling dungeons. Or else you're just making this game more toxic than it should be.