What are you trying to accomplish?

I am not sure what you mean about PvP boxing as a group, not sure that will work out others could comment better.

If your not going with WoD, I am not sure what the viability of 10 boxing would be. One level 100 character should be able to Holy Nova your whole team to death.

Gearing is simple, use leveled Heirlooms and you are done until 100, there is a real lack of grind until 100. Once you get your toons at 640+ and a trinity or more higher (LFR and garrisons) you can do some PvE raiding in WoD pretty easily without much fuss if you know how to work your characters.

I would advise leveraging dual specs as muc has possible since gear has spec stats now (unless your not doing WoD). While a hunter, mage, warlock are fine, dont cap everything that way. This will also help grinding in queues.