The biggest problem you will find when you get to Outland is that an instance run isn't nearly as large a chunk of exp as it is in Azeroth.
The levels take a lot more exp and the instances are, for the most part, shorter. Where a full ZF run will give you 1/4 to 1/3 of a level at 47, a full Ramps run might give you 1/6 to 1/10 of a level at 60.
Basically you'll be running the instances a lot more to get those levels. Then, once you get to level 66, you really can't run any more instances until 67 or 68, depending on how good of a healer you can find for Sethekk halls. You could keep running Mana-Tombs and Auchenai Crypts, but IIRC the mobs cap out at level 65, so you won't be getting nearly as much exp.
I am leveling my pally prot the whole way (from the first talent point I could place I have been prot, and I will stay prot at 70). It's definitely doable, but you will be better off mixing in some Outland questing with your instancing. At least do all the quests in HfP and Zangarmarsh, as everything in Terokkar and beyond will still be green at 70, very easy to solo with a prot pally, and worth a TON of gold towards your epic flyer.
Edit: My recommendation would be to get to 60 in Azeroth by tanking instances. Go to HfP and run Ramps and BF until you are 61.5, then do all of the HfP quests. Move on to Zangarmarsh and do SP and UB for about a level and a half, then do all of the Zangarmarsh quests. By this time you should be of a level to do Mana-Tombs and Crypts and mix in some Terokkar quests if you want.
Edited, Apr 22nd 2008 8:53am by Bigdaddyjug