There really is no "our" badge gear and "thier" badge gear. There is just badge gear. If there was badge gear that belonged to certain classes, the mage would be asking why "ours" has so much crit, as mages(especially fire) love lots of crit. Besides, reaching the Hit cap through other pieces and gems is easy enough.
As for what to buy, I'd save your badges and make money off them. In the beta now and I can say that while some pieces may make it slightly easier, there's really no point. There's also a tailoring set that you can make immediately upon reaching Northrend(if you buy the mats), that has more spell power than my current 2pcT4/2pcT5/badge Crit Chest setup. It has more Sta too, plus good amounts of Spirit, which we will need. It lacks hit, but that's not needed until your raiding anyway, it also lacks crit, but if you level Affliction, until you get Pandemic it does no good anyway. Seems to me that that will be the way to go starting off in Northrend.