From what I could tell yesterday in the 10 man there's 4, basically 1 portal in front of each of the 4 NPCS if you have them helping you. We were going in with 3 dps and 1 hybrid dps (shadow priest, ret paladin, boomkin whichever we had) and the hybrid would help heal in the event people got low.
i think 30% is the transition to phase 3, we were able to consistently get him to phase 3 after 3 portal phases. using melee to take the portal.

