I strongly suggest TankSpot re-make the 10-man guide.
Out of all combinations, the toughest would be those with 2 healers in the mobs. Although the strategy is about the same as 1 healer, i.e. to cut down the healers as fast as you can, the mechanic of the fight is dramatically different. That is because you need to find a reliable way to CC the 2nd healer while you are fighting the first one and dodging others mobs (or eating up their damages). However, that is not simple at all. As we all may have seen, most CC methods don't last long and PvP-styled diminished returns come into play here too.
One thing that would definitely help is the raw stamina of every team members and their gears, of course, the higher the better. The guide would be much more informative if such minimal requirement on gears/stamina/resist is suggested.
(PS. I haven't seen any 3-healer packs.)