Our fury warrior found he got around the same dps from offtanking due to the extra rage/heroic strikes he could complete so I'm not sure of the advantage of NOT going 2.5 tanks there. Also interested to why you ran with 2 disc priests, when holy pretty much owns that fight.
I do agree that kiting's not needed, we simply spread and burn (and usually finish up with 8-9 alive). Not sure why you're having to use CD's like barrier though, just PW:S everybody, the dot ticks for 2k/sec - weakened soul on a >30k shield is 15 seconds, so the debuff won't even tick for your group.