I've been averaging 100-120k xp/hr just doing non collection quests and instances mixed up (with 5x shamans). I can complete an entire zone of non-collection quests in like 6 hours since things go so fast, so that helps a lot. I ran all of zangarmarsh with my 5 shamans minus the collection quests in like 5 hours. Once I hit 64 I had to stop a bit to run BF/SP until I hit 65 and now I'm in Nagrand at 65, hoping to hit 67 by the time I'm done with Nagrand + more instances. Then I'll probably run mana tombs a bunch to hit 68 and then durnholde to 69, then I'll finish up quests to hit 70 and also do a bunch of extras for the gold. So far I'm only averaging around 6-7 hours per level which is super fast.