Hey . I realized I normally don't post in these after we've gotten a boss down, but I decided to do it this time in case it's helpful to anyone looking to down this fight in the future. Here is our healing done for our kill:
We used 3 healers: myself (rdruid), a holy paladin, and a disc priest. Disc priests are excellent for this fight, because they save us tons of mana by pre-spirit shelling before the unseen strikes.
It was pretty close -- you may notice if you look at the damage done that i did 830k damage with wrath. That was me spamming it with heart of the wild at the end and we only just barely met enrage (right as he died it said he enraged). However, I think as people get more experience with the fight, healer dps will be unnecessary.
As someone mentioned before, putting heals on people before 20% is good too for healing up the damage they take from the unleashed storm. Our paladin popped holy avenger and spammed eternal flame on people, I spammed rejuv, and the priest spammed shields before that and it helped a lot so we didn't have to heal as much on the way down (I did hit wild growth once or twice on the way down and kept the stack of lifeblooms on myself, though). We got across with 2 savage roars and it worked out pretty well. I did sprint at the end, but I probably didn't have to since I had to slow down when I got to the end, waited for the whirlwind to spawn, and then ran up. Cat form was still great for making sure I ran up quickly, though.
The advice given by someone earlier in this thread to run with the wind down the sides (be careful not to ride the tornadoes back because they will shift direction in mid-flight if he hits 10% while you're in one) was great. We too sacrificed a DK tank that stood there and did the remaining dps in addition to the dots on the boss as we all went to the other side. We found leaving at around 12.5% was perfect timing, but it may be different for you depending on your tank's dps and the amount of dot classes you have.
Also the advice given in this thread to just focus on getting to the end and THEN popping your healer cds was great. When I concentrated on getting to the end instead of healing people on the way (they used personal cds and healthstones), I was able to get to the end and pop tranquility.