As a hunter, not a single death during leveling due to mobs (hit 85 at 8pm tuesday - EU). Usually killing 3-4 mobs at a time, 2 on pet, 1 on me kiting, one in trap if necessary.
I got realm first warrior (2pm Tuesday) without pulling more than 2 mobs at a time. The questing is designed so that you don't need to, and the only issues I encountered where when, as people mention, you kill a mob and another respawns in it's place.
There is no need to level like that and especially in Twilight Highlands you will get battered if you pull more than one mob at a time.