My normal RAF boosting method is:

RFC --> ***SFK*** --> RFK --> SM:GY --> ZF

I hit 55 in three days on my shaman. I used a geared arcane mage (before the "base %" mana consumption change for arcane blast). I've since then used that same mage as frost and it's actually easier, with ice barrier and all.

Account #1: Mage, Shaman, and others
Account #2: Shaman
Account #3: Shaman
Account #4: Shaman
Account #5: Shaman

Use 1(Mage)+2(Shaman)+3(Shaman)+4(Shaman)+5(Shaman) to run instances, then grant levels from #2(Shaman)-->#1(Shaman). That way your entire group stays the same level. Can't remember exactly how it worked for me (since you get to grant a level every other level), but it did.

Shadowfang Keep is very nice. Never tried Deadmines, but it seems like it would be just as easy. The kills only have to be in proximity for the XP to count, and it seems like gathering all the mobs on the boat would distribute XP to the slaves no matter where you're at in the instance.