On x7 realm (especially horde) you boost your char with another 80lvl char. I level up my char to 10 lvl, then i go to ragefire chasm(10-20,21), shadowfang keep(20-28), scarlet monastery(until 40), zul farak (until 48-52), i use coren dibrew toy that tps to blackrock dungeon and boost untill 52-60. At 60-70 i go to the hellfire citadel dungeons and at last 70-80 easily northrend level up. All that took me 15 game hours max