Yeah, we basicly run 9 healers on Felmyst. And 5 priests. It just makes it so much easier. As for Encapsulate, the trick is to have a sort of square setup on your group spots. And one group in each corner. You have to position so that there is a healer on both sides of the "square". Also, very important is to note that healers from the group next to you should be able to reach you.
(scale is off, groups are far enough from eachother to not hit the adjacent groups with Encapsulate.)
We also had a Prot Paladin in melee, dispelling the bottomleft group (which were 2 healers + affliction warlock + MT). Your groups need to know EXACTLY who is where. So as soon as the target for Encapsulate is known, they know where to run. And everyone that can remove it, should. You absolutely also have to be on full HP when Encapsulate hits, it's a killer.
For our first kill, we used Arcane Protection Potions. You can chug them when you're encapsulated (as can you use healthstones, by the way) and if that's not enough, use
[Battlemaster's Determination]. Those trinkets are such a big help, it's quite the lifesaver.
Also, important to know that she does not keep hitting the MT whilst she is channeling Encapsulate. Not to mention that she will delay going up if she is late on the casting of it. Which means your MT healers can help out (they should be in range of most people, really).
As for phase 2. Use one person calling out the direction where to run. Don't argue. Trust that person. Even if he does fuck up, it's pretty annoying the first few times. Besides that, we have always used a prot paladin on the skeletons, it really makes it a nonissue.