I have 4 shaman and I sorta boosted them from 20 - 40.

I honestly didnt feel like I was leveling faster with the 70 in my grp vs just going at it with the 4 shaman. The one thing about boosting is that its very mindless so in that regard its nice if you just dont want to think or try. But thats not really why I play so I didnt find it very rewarding.

Also and more importantly - the lower lvl instnaces are a lot easier (no AOE silence on melee bosses that will face you with cloth and leather gear on) so thats really the best time to learn how to multi box. I am still learning how to do stuff but I def think that people miss out on fundamentals when they skip low lvl stuff.

That said if you already learned everything you think you need and you just want to get it done without thinking and feeling like its a lot of work then you should boost at least to lvl 50 or so.

The other thing you can do it just offer to pay someone 10g for a run thru. You probably make that much in greens and blues anyways. I have done that too - its one of the few times I actually pick up all the stuff of the mobs.

anyways GL