So you’re a new WoW player, you’ve leveled up a bit, maybe even to 90, can handle the mobs you’re running into, and so decide to enter a random dungeon (because you’re brave, or foolish.)
So you get the group that want to clear everything in 8.3 minutes, skips the looting, and his hardly tolerant of people who can’t quite keep the pace or who don’t perform exactly the way the group demands.
This is what the Proving Grounds are for. The Proving Grounds (PGs) are there to help you train yourself, or prove yourself, in a series of encounters of increasing difficulty, without the snide remarks. No worries about being punted from the group.
All you have to do is be level 90 and be able to get to Kun Lai.
Personally, I think all my characters will be giving it a workout. If only to get used to a new set of abilities after playing some other class for awhile. This should be far more useful than the target dummies.