Triple Healer.

This is a very easy combo. Your healer should be able to heal with very little assistance from you through the 2 dps dmg. Next is identifying the softest target. Like this and the 3 melee combo shaman are always smart to take down. Grounding totem or Windfury + Warrior and Bloodlust will make the fight tough.

I kill most druids with a lightning bolt Chain lightning combo. The fight usually goes like this, warrior charges, followed by another charge, followed by 2 fears and a mass dispel. After you apply some dmg to the warrior the Druid will pop and attempt to cyclone your healer. Even though this isnt a caster dps keep those grounding totems up. The second the druid stands in the open I kill him. I intentionally tell my healer to stand in front of me so when he does pop I can take him out quickly. Apply pressure to the priest, he'll blow Pain suppression and run. If the pally is standing in the open, give him something to heal (throw some dmg on the warrior) and then light up the pally.

On the triple healer combo you just have to make sure you dont sit on one target. When you do kill one of them they can't recover and its gg. Shaman are the most dangerous in this group (WF totem and grounding totems will make your life hell - if theres a shammy take him out). If the warriors get to far in front and you have a chance to light them up its gg as soon as one of them goes down. The key to this fight is to put pressure on the healers so they run for their lives and kill the warriors while they dont have 3 healers pumping them up. If they aren't dying their being healed, find the healer and Lightning bolt Chain lightning combo them. Healers get very scared at 25% health and have a tendency to run.