When I hit 60, I jumped right into outlands thinking my 5 shaman would do just fine in the instances... After first couple of pulls and first boss, I was told otherwise. So I went to Wowhead, pulled up all the quests in Hellfire that dropped mail caster gear and just went to town on all those quests. After I completed all of those quests, my shammy's were in solid mail gear and at level 61.

I jumped right back into Ramparts for another round and what a world of difference. Started clearing Ramparts and up to the first boss in Blood Furnace and stayed in those 2 until almost 64 since the xp was easy. Then I started throwing Slave Pens and Underbog into the mix and before I knew it, I had Earth Elementals and it was smooth sailing in instances to 70... Not always the fastest, but to me was definitely the easiest... Hope this helps!