Atm they just synergise the best with each other, both (almost for traps) spammable CC and extreme mobility. Druids don't have to cast to heal where other healers do on top of that. Nerf swiftmend and get a small cooldown on cyclone will get things fixed and tone down druids a bit. Still every healer needs a bit of a survivability buff then so that 3's won't be a NUKE-THE-HEALER race. The amount of brainless double melee teams is too damn high!