Its an interesting idea, but I don't think it has much potential. Multiboxing Melee classes is awkward, and at some point each of your shockadins have to melee... 5 Concencrates sure would be nice tho.

My PvE group is comprised of a Prot Pally, 1 Priest and 3 Mages. I routinely farm Pre TBC instances by running through and frost nova + concencrating every time my concencrate cooldown is ready. This locks the mobs down into the concencrate (building all aggro on the paladin) while the group moves forward to aggro more things. The Priest rotates HoTs to keep everyone topped up, and when Im ready to burn things down I wait for it all to get to me (Line of Sight FTW) and Concencreate + Arcane Explosion everything down. Works really well.

I have less success AoEing with this group in Heroics, I regret not rolling 3 Warlocks instead, as Seed of Corruption is more multibox friendly than Blizzard.