2 healing everything is fine but you would need strong healers no doubt. Personally my guild have 2 healed 11/12 and will 2 heal lei shen too. I would also like to mention that any 2 healing setup without a disc priest will struggle a lot more because atonement is just such good passive healing in a close to no damage phase which makes both your healers have close to full mana when the action starts. Having a Rshammy or Hpally with them is probably the best too.
For your group though i would say 3 heal all the way, you have way to little gear and not a good 2 healing setup available. Just make sure that your dps does their job