Okay I'm level 45 now, 20-40 I was run through SM, and I've been run through ZF twice now for the quests. I will probably get run through ZF a few more times yet, but-- looking to the future, which instances should I get boosted through, at what level, and which classes are best for boosting?

I've searched through a bunch of the old threads but haven't found anything concrete.

After ZF where should I look to for boosting? At what level? What are the best runners?

ST?
BRD? Prot Pally, Fury War?
Strat?