I just respecced my Rogue (3rd alt) to Combat from Asass last night. I only did a bg and a few guildie duels and I gotta say I like Combat alot better.
I keep hearing conflicting information though, about what the best pvp/arena spec will be next patch.
Ive heard Sub is getting big buffs and will be best and have heard the same about combat.
I havent played PTR myself.
(Not sure if this should be in the pvp forums)
Getting you're opponent semi low will make killing spree almost like a rogue execute. It's a pretty fast high damage ability that's really hard to counter. Adrenaline rush on the other hand is pretty easy to get CC trained through.
One of the biggest draw backs to combat is the lack of haste on pvp gear and it's reliance on that stat. Combat, unlike sub and assassination, has no built in energy regen component. Assassination if you can rupture 1 or more targets your energy regen is about as normal as it is in pve unless you stack go pure haste like some rogues do. And, sub is the same way. As long as you have SnD running you have your energy regen mechanic working. But combat just relies on haste for that so the lack of pve gear's haste is kind of a let down.
Also restless blades only works off of evis/rupture and in pvp you're stunning and using utility instead of pure damage a lot more which greatly increases your down time on CDs. Where in pve you might have a 40 sec-1 min cd on ksp it's closer to it's full duration in pvp.
Also it lacks the utility that sub brings with shadow dance.
With assassination it just has a long ramp up time compared to the other specs so that sucks. It's sustained is probably the best of any spec though. Sub has premed to start off with SnD in stealth and then with subterfuge you can open with a stun, garrote for sanguinary veins, and ambush and have every buff you need for maximum damage right off the bat. Combat has a long ramp up for bandit's guile but that's more of a timing thing for CDs and for the most part combat is at it's damage thresh hold once you open and get revealing strike/snd up.
As stated by the OP, combat is fine for some deuls and BG's. It's when you get into arena that it becomes hard to excell with. The heavy reliance on CD's means that if you get CC'd during them, you have nothing to fall back on. I tried it for awhile and the KS nuke is fun when it works, not so fun it doesn't. The upcoming higher energy/higher damage SS will only exacerbate the problem.