I often take the crystal as the tank, it's entirely doable, i just pay attention to the timers, stand in yellow range so the soaker can be closer to me, then dance in for blue when the stomp happens, but really, you should be fine and by far an easier way to do it is to 4 heal.
The fight is designed for 3 healers. The kohcrom side receives less overall damage throughout the fight and is designed for one healer to do alone. You can use 4 if you want to be safe...but the 2 on kohcrom side will probably be bored.
Doing the morchok side solo is possible. But if that healer cannot do it, its because that's not how it was designed - not because that healer sucks.