i have played the Sorc and now i play Merc and healing using Merc is much simpler for me because i can manage my heat better then the Force. The Force depletes fast and what then no heal let me take to regenerate my force?
In Merc class i have to 2min CD Heat reducer but even when i have high heat i can still heal for small amount without pauses. Yeah the problem is when it comes to 1 Healer more then 3 to Heal and if they are scattered the efficient healing is gone, you can heal 2 people i n acceptable pace. please also understand that i haven't done any OPs yet just Flashpoints
on the other hand merc is an bodyguard so it combines firepower an early 4 AoE damage with healing so its very good with group that don't need every sec healing to stay alive and still need that extra fire power to slay down enemies with speed. (i just love to see the power of 2-3 bounty hunter class AoE in action so much damage in such short time)
If we wanted to make mercenary a better healer is to make the kolto shell accessible to all of your group (now it is just single target only) but that would probable made soma balance problems with other Sorc and OP