From the record, I'm level 29 Merc Bodyguard and new to PVP, so obviously, a total noob.
I really like PVP, but man, it is tough playing as Merc Bodyguard compared to Scoundrel/Operative healer. The stealth and instant cast heals are huge difference makers. As a level 29 Operative, getting 100+ K heals are easy, especially when I don't have to worry about dying. As a Merc Bodyguard, I die 4-5 times a match, heal around 75000K and do some damage. It's fun, but endless ganks. I do try to stay away from the action and move after a few casts, but it helps little. The Force users all move in fast and I'm dead 1 vs 1. I do have points in power shield and protective field, but it seems to only put off eventually dying anyway, especially when it turns into 3 or 4 on 1.
And honestly, when you get a few mvp votes and around 8-9 medals sometimes, it's motivation to keep trying.
Any advice other than you suck because you don't heal for 300K? (which I have never seen in the 10 or so warzones I have played)
Bodyguard/Combat Medic really takes a while to come together -- you really start coming in line right around level 30 and are pretty close to fully powered at you enter the mid 40s. I guess that qualifies the AC as a late bloomer? Once you get your 31-point skill and start getting some of your heat maintenance options, you should be able to survive longer on raw healing output. Lowbie is rough in my experience as any healer until halfway through the leveling curve, just because DPS tend to get their key abilities and procs sooner and there tends to be ALOT of deathmatching in lowbie (two ingredients which make healing a pain in the neck).
Let me put it this way, the class has the highest learning curve of the healers but eventually becomes the most durable of the healers. It just takes time, experience, and gear.