I once read somewhere that the experience you need from 60-70 is the same needed to get from 1-60. Going off this, in theory it should take the same amount of time. This is incorrect for me and probably most others.
At first, Outlands are great! New, Spiffy quest rewards, lots of exp from quests and mobs and new instances to explore. As long as you know how, you can level to 70 easily. If I spend a lot of time on it and constantly do what I’m about to tell you, I can make about a level day, maybe a little less. Which I think is pretty good going, it’s tough to stay focused and stay on target.
First of all, it’s important to stay rested. It pretty much doubles the speed that you level. Second, do a mixture of quests and instances. Otherwise, you’ll get bored and won’t bother. Do Quest after Quest after Quest. No pussyfootin’ around in between. Whilst you’re questing, stick yourself in LFG. No point in deciding you want to go to an instance and having to wait half an hour to form a group.