We have discussed this before on sindi threads remember the longer the last phase goes the more likely failure is.
By stacking in close to the middle everyone inc healers can hit her like pally healers dropping consecrate and anyone who needs to dump the magic buffet doesnt have to run a mile to hide. Save all cd's for the phase and launch pets and even healers dot etc.
I am not a great fan of everyone running to tombs thats a metric ton of dps time lost. By far the easiest way is to have one dedicated dps to break the IB's with a backup who does it only if the breaker is the target of the IB. The break rate can easily be controlled by 1 person anymore than that and it gets popped too fast or slow.
I would agree with everything fledren has said really just adding the blow CD's, launch pets and healers use what they can as well you want the phase definitely as short as possible.
** Remember Warcraft players fail in directions you never thought possible.