Ok this mob is more complicated than the first two, but once you get the hang of it you should enjoy it.
First thing, this mob requires two tanks, and you'll need 1-2 ppl to pull adds to the raid.
You will notice that Sara is in a little room to the side of a larger circular room. This circular room has side rooms just like Saras. Before you pull Sara make sure the side rooms are cleared.
Now how we did it. We had the whole raid minus the two tank and two ppl against the back wall in Sara's room. The MT pulled Sara pretty much were she stood standing against the table. OT Stood next to the named the whole time.
Now things you should know.
Sara has three ae's
Arcane Shatterstorm approx 33 sec timer. Magic damage. Its a dot so cure it!
Cloud of Confusion approx 33 sec timer. Mental damage. Its a dot so cure it!
Mists of Lethargy approx 33 sec timer. Poison damage. Its a dot so cure it!
Now one of the ae's has a knock up and back with it thats why you are against the wall.
How to kill this mob.
During the fight you have your 1-2 ppl running around checking the circular room and the side rooms for a defiled bloomling. There is usually two up at a time. If you fail to find these mobs bring em back to the raid to kill they will span into a x4 twisted mossfiend, which just makes the fight even harder.
Now these bloomling will spawn in the same room as you, so pay attention if you see em target em and kill em. Make sure you are comunicating on how many are killed so you don't miss one and it turns to a x4 mob.
Other than that the only major thing with this fight is when the red text appears it is time to switch tanks. When you do the switch if the new tank holding the mob dies the old tank will get one shotted. So keep your tanks up. Also old tank don't pull agro. If you need to, stop DPS altogether. Both tanks will have ample amount of time before the switches to rip agro back.
So over view of this fight. Switch tanks when red text hits your screens. Don't let the tanks die or pull agro. Cure the dots, Kill the adds before they spawn into a x4. And just burn the named. If you have a strong group for the adds you should be able to drop them very fast. Thus leaving the rest of your raid on the named to end the fight quicker
Enjoy the loot.