We did this fight on Wednesday successfully and I will shed some light on the encounter for you all.
First off, after 2 GS are cast on her, she becomes immune for 1 minute to them. So you need to use them wisely. I like to pop two at the beginning and then each time after healers come out of the portal.
My healer makeup for this encounter was...
2 resto druids
2 holy priests
2 holy paladins
1 resto shaman
In my guild, we popped heroism right at the beginning and got about 13% healed up right away. The reason we popped it at the beginning is because it the most amount of time everyone will heal the boss. FYI you can bandage her (lol).
We had the Paladins and the druids the only ones entering the portals for the healing buff everytime. We alternated sending in the priests for the mana regen. The shaman just stood out there healing the raid.
Sending in all healers at once is a stupid idea because then there is nobody healing the raid. Once you enter the portal, you are stuck there for 20 seconds. You leave the portal and have about 20 seconds of raw healing on her and the raid.
The only ability you have to cleanse off her is the disease. You need fire, frost and nature auras up. Make sure those suppressors get taken down ASAP. The only debuff you should be cleansing off players is the disease on the tanks also. Don't worry about the frost volley debuff. It's just a slow for 4 seconds (not a big deal).
Most of the time, I would throw renews, SoL flash heals and binding heals on her and just heal the raid up.
The key factor is making sure you chain the buff. If it drops off for w/e reason, it will probably be a wipe.
As long as DPS and tanks can control the adds and not fail at raid mechanics (aka void zones), this fight should end quickly.
Here is our WoL parse if you are interested. http://www.worldoflogs.com/reports/e...=10362&e=10766