The Merc Bounty hunter is going to be a great healer.
First off - the heat system they use is incredibly efficient compared to some of the other resource systems, specifically the force system of the inquisitor.
Second - Kolto Shell. This ability is similar to a WoW shaman's earth shield which is incredibly effective cost/output.
Third - Emergency Scan. Their top tier talent is an instant heal and a big one. Those that have played MMO's will realize how crucial an ability like this is to healing.
Where other healers will have the edge on them is in AoE healing. I believe Merc's will be very effective tank healers and group healing will often fall to the other classes in raids.