Having 3 dedicated people at all times will maximize the chances of stacks because having 2 teams switching only gives us 1 chance of enhanced healing once every 50 sec. (35sec then a 15 sec wait period between the diff. teams alternating portals). Buy having a dedicated 3 it gives us about 5-7 sec when entering the portal to initiate another stacking phase. Also being in range of someone getting a green cloud buff also "splashes" for about 3 yards around so u can get the buff with out actually flying directly into one. I may try auto follow just to see if I can rack up max number of cloud with out having to fight for them. We also have to put in affect Lay on Hands for the ret and prot pallies to maximize healing.
Other than that me and my guilds healing crew was pumping 8k HPS on average. 8k HPS*240sec(60sec*4=240)= 1,920,000 healed for one player in a 4 minute fight. That times 6 healers is 11,520,000 healed. If just 3 dedicated players hit all the clouds we will get it done in 4 or so minutes beating the extra waves of adds