One last point on this old post , if you level the toons you are granting a level to REALLY close to the next level when you grant them levels to 60 they will be still x amount of XP from that level and so it is real easy to get that toon to 61.
Also it is still well worth boosting toons in the ramps and other Outland instances because you can bring them all into the instance with not a very big hit for having the extra toons in the instance and so you can blow through 60 - 65 and even get to 70 via boosting in dungeons. I have done this several times and it makes it a lot easier than dragging toons around outland.