Simplest solution is probably pala tank/4 shamen to heal/dps for dungeon running. Pala tanks are hands down the multiboxer tank of choice(Though warr/druid works too, requires a lil more micromanagement, + blessings/bop/bubble/DI are nice :p)

However your pala's pretty low lvl...you can either
A: Roll chars and lvl naturally with pala tanking + alts caught up to his lvl and continue on normally, taking advantage of the time spent to learn how a pala tanks as you progress and have little issue later on
B: Powerlvl the Pala with your Mage or Rogue(Mage for SM/aoeable places, Rogue for the harder places if you're careful since Rogue can survive better + escape if shit hits the fan)

I'd lean more towards A, almost exlusively for the Tank/alt control experience factor...but I'm also impatient and I'd probably plvl them to at least 30-40+ then worry about learning once the pala has Plate + all his good tank skills and gear to support it lol

IF you're good at Micromanagement, you can slip that Mage into the group for CC options later on too...the Rogue's pretty useless though for anything but powerlvling, Melee doesn't work well for us if it's not the lead char and if pala's tanking, the rogue ain't backstabbing or dpsing optimally, they're micro-heavy if you want full performance lol

Warlock's on same account as Pala so he can't do much powerlvling forthe pala, but you could always use him to catch up the non-pala chars. Hunters are great for soloing but for a boxer unless you're going all hunters or getting a BM tank pet(Which wouldn't work well enough in Outland instances for most bigger trash pulls), they're simply not worth it in most cases.