Spoils of Pandaria - LFR Multiboxing Bug

I don't understand how this is directly caused by multiboxing?

I boxed it without a wipe a moment ago, but with different b-net accounts. Don't know if they fixed it yet.

I can split the raid and do 5 on one side and 5 on another, but I cannot do 10 on one side. If I put 10 of my characters on one side it wipes the raid. I've done this with the following.

1 Prot Paladin, 2 Holy Paladins, 7 Ret Paladins

and

10 BM Hunters

I haven't a clue what causes it, at first I thought it would be melee stacking, but alas, 10 hunters... still wipes...