First of all, I really would like to remind everyone that hellfire cleansing Dark Touched is getting fixed next mini-patch (
WoW-Europe.com Forums -> 2.4.2 Patch notes (Update 25/04) ).
My own observation regarding the shadow images, I can tell that first week we did it with Sacrolash tanked up top, the images didn't last enough to be an annoying factor during the fight, they despawned before they reached the raid. However, next raid that wasn't the case, they were actually reaching the raid and stunning healers, so we changed the healing assignment a bit to have druids hotting tanks to allow them to survive the stun and have a solo healer standing away from raid.
Now we're using the tactic killing Alythess last, and we're still using the druid hotting tanks method since stunning is still issue here, I think it's something you have to heal through (or if you're really having issues, maybe have Free Action potion rotation going?)
Another note on Shadow Images, their Dark Strike attacks are mitigated by resistance, so buff shadow resistance.