I play as a survival hunter as I like how dmg flows with explosive shot. But if my only purpose was to kill healers, then I'd spec Beast Mastery. This would enable me to have multiple disables: 1) Spec Stun, 3 sec; 2) Different pet abilities- monkeys, moths, mosquito (different disables variate between 2-3 sec stun, to 4 sec disorient or interrupt cast and webs); 3) Scatter shot. Combining this you can have more than 8-9 seconds of disable, not to mention the fast shooting rate (can have multiple haste rating items).
Although I don't prefer this type of play because of subjective reasons, I have done it, and it works.