Personally I find that being engaged by 2 melee in PvP is a death sentence, especially on half HP. I don't think I have yet to flashbang someone who hasn't broken it. There are millions of CC's charges and snares that will destroy you.
A few tips that might help:
If you're being pursued, turn and use your snare. A lot of people break this, and you can use debilitate or flashbang after that. I strongly recommend you take the debilitate talent in Lethality, the 15 sec reduced cooldown and speed boost are surprisingly helpful.
Tox Screen can get rid of some snares, and annoying dots. Plus when talented it grants a heal that I've seen crit for around 1k sometimes. Not bad to use on the move if you have no TA for surgicals.
Keep moving, snaring, stunning. Make sure your hots are up. After that it's a matter of Surgicals and Tox Screens, and hoping your team values healing.
Injection is only really viable around corners or when you have a second of safety after CC.