Hello guys, time for my first contribute!
If your for some reason fail to kill sindragosa the "first" week, using this method will let you to keep the quest item from Valithria and do the quest at the second week (this means if you manage to kill her the second week, you get the sack from the previous plus your current on the same week.
I discovered this last week when doing ICC, i will try to explain it the best i can.
Step1: Go icc and do your business! And wish that your ID will get the quest from Valithria Dreamwalker (Respite for a Tormented Soul - Quest - World of Warcraft)
Step2: Lets say your guild isnt good enough for Sindragosa and your raid ends there. Dont worry, engage Sindragosa go pew pew her until she is weak and start channeling your [Pulsing Life Crystal] and at the same time you abandon the quest from your log. Now die :> The crystal will stay in your bag and Do NOT delete it.
Step3: Now its another week, new reset. And wish that you get another weekly and not the Sindragosa quest. For example ive got the Rotface+Fester quest, complete it and hand it in. Now go Sindragosa and this time succeed to get her down (Yes, channel your Pulsing crystal) and tada the quest is back in your log and is completed.