Bodyguard:
This is the healing tree for the Mercenary. The Mercenary is a fully capable healer, able to successfully heal in PvP, Flashpoints, Raids and World PvP. The Bodyguard needs to be a little more proactive as a healer as compared to the Sorcerer or the Operative. Most of the Bounty Hunter's heals tend to have long cast times, requiring him to stand in place. If the Bodyguard falls too far behind in healing, it can be a bit difficult for him to "catch up". Alacrity is an important stat for a Bodyguard as it will let you cast your heals faster.
Bodyguard specced Mercenaries have successfully healed throughout the end game in beta. They do have a few problems - namely their primary focus in longer, powerful heals. This makes them fairly stationary. They also tend to run into problems if you "fall behind" on your healing; it's not as easy for them to catch up as it is for other classes.
The two major benefits for the Bounty Hunter healer are that first, if you manage your Heat correctly, you will always have the ability to heal, and second, your Combat Support Cylinder changes your Rapid Shots so that shooting your allies will heal them. This gives you a quick, no-Heat cost heal and is useful in times where you are required to be extremely mobile. Of all the "free heals" that the healer classes get, this is certainly the best one.
Many people suggest that the Sorcerer is the best healer, and in some ways they're right. Their Resource system is a lot more forgiving than the Bounty Hunters. If a Sorcerer has to spam burst heals, it's not a big deal. If a Bounty Hunter has to do the same, he will drive his Heat meter up into the slow dissipation zone and have difficulty regaining his tempo.
But, a Sorcerer will inevitably run out of Force points for healing, whereas if a Bounty Hunter is careful with his Heat, he can potentially heal forever; still, this might not be a huge benefit. Most end game bosses have strict enrage timers, so even if a Mercenary could heal for 20 minutes straight, it doesn't mean that he'll ever realistically be able to do so.
Still, as pointed out earlier, Mercenaries have successfully healed all of the content in the game. If you want to play a Bodyguard, more power to you. Don't let people tell you that you're going to be a fail healer or useless at end game. You won't be.
Talent Skill Notes:
Kolto Missile: It's not a fantastic AoE heal. You won't be able to get by in instances just spamming this ability. You'll frequently find yourself using it more for the +10% buff on targets than the actual heal. You'll generally want to keep the buff up on the tank at all times.
Supercharged Gas: An important ability for the Bounty Hunter, Supercharged Gas changes your playstyle a bit when you activate it. Getting 30 charges of your Combat Support Cylinder isn't too difficult. You can shoot allies during downtime between pulls or before the start of a PvP match. Knowing when you use this ability is very important, especially in PvP. While it does allow you to spam Healing Scan, keep in mind that you'll overheat very quickly if you try to do that.
info found at: http://blackrabbit2999.blogspot.com/2011/12/swtor-bounty-hunter-beginners-guide.html
and my personal choice for OP healing: http://www.torhead.com/skill-calc#300rfRMR0cdkqZrcoZb.1
