Brace For Imact
Devidan Sub Space thingy
Aux to Sif
Aux to damp
You should be able to combo any 2-3 of those skills to completely laugh at any single ship alpha strike. If you can't then you need to l2p.
Burst in this game has already been nerfed to a point where an average match will be 30+ min.
If you are consistanly getting roasted by Defiants then its your issue, not the def-r.
Everything worth saying has pretty much already been said.
Defiant-R is a hit and run machine.
As a Defiant-R Captain, I'll look for the easy kills in a battle or the people who aren't spec'ed correctly, and hound them mercilessly. I'm an opportunist. I look for someone whose blown a ton of cooldowns or who isn't paying attention to that low shield facing while they're mixing it up with someone else. Make yourself an unsavorable target, and you won't get hounded so much.
If you're getting blown up constantly by an escort, you need to take a long hard look at what you're running and what abilities.
As a Def-R pilot, while spec'ed fully for hit & run, I only get kills within 5 seconds if the opponent is inexperienced, unprepared, and/or distracted by my teammates. Otherwise it takes about 10 seconds, or I have to run if I've failed to kill my target - which gives you plenty of time to defend yourself. There are plenty of counters to alpha strikes. A combo of Tac Team & EPtS as soon as you hear someone cloaked popping of their powers or even immediately after they begin firing at you works well for me. Other tactics mentioned above work well too, such as FBP, tractors, RSP, or good old-fashioned teamwork.
A hit & run defiant that can get quick alpha strike kills are glass cannons, and therefore are very squishy and easily poppaple. The only tac captained defiants that can tank well have to sacrifice burst damage. I know because that's how I used to have my defiant spec'ed and I rarely got kills in my first wave of attack. Engineer captains can tank their defiants well, also with a sacrifice to burst damage - and therefore making it difficult to get 5 second, one salvo kills.
If I didn't run after being damaged & focus fired, I would die quite often in PvP.