You will actually breeze through all of Outlands many grinding and collection quests with the help of your 70. I had absolutely the worst time trying to level my warrior solo through Outlands, no matter what talent spec I was using or how great my gear was, I wish I would have waited until I leveled up the rest of my toons to help. Even solo'ing elites was almost impossible for me.

Because you are only dual-boxing, you don't have to suffer on collection quests, and you can do a lot of the group quests on your own. I would set the Warrior as main, and the Hunter as the secondary. With the help of Quest Helper, I would run around and grab all the quests I could, and knock them out as quick as possible with the additional DPS from the Hunter shooting from a ranged distance, and the pet. You'll seriously fly through most of your quests, and your Warrior will hit 70 before you know it.

Infact, the only way I leveled as a Warrior was with the help of my girlfriend who plays a Hunter who hit 70 before I did. From 65-70 probably took us 10 hours (playing about 2 hours a day.) And alone, unrested, I was usually only getting .1% for each mob I killed, so the main source of exp came from turning in quests, so it was totally worth losing a little exp from killing mobs as a group compared to killing them alone.