Each person that gets hit with insanity creates a clone in every other persons insanity. So if you don't use the LOS trick then each person will see 4 fakes of the other people in the group.

1 will see 2,3,4,5

Once 1 kills all of his 2,3,4,5 he will enter someone else's insanity (seems random) and can help them kill the remaining ones in their group.

Until finally all 4 fakes in each of the 5 groups have been killed.

My group is a druid tank, resto shaman, holy pally, shadow priest, hunter. Hunter is my main. I drive hunter, priest, shammy - Friend runs druid and pally. The shadow priest has a targeting macro that assists my hunter. So while I am killing the ones I can see the shadow priest will also target his assuming I am targeting one he can - He won't kill himself, and I don't target myself. My shammy and pally are self healing to keep themselves up throughout the event. Me and my druid buddy will kill all of our adds, then help out the other toons.

Honestly though until its called an exploit I will probably LOS it. I know they have said its not working as intended, but yes they can easily make it hit you if not in LOS, hell we have done tons of encounters using LOS. If they don't want us to use LOS then arenas are in for a BIG change.

It was by no means easy, but I think the first time we did it friends toons where 73 and mine where 74 at most.