Now, I'm not exaggerating here, on my battle group, the Horde wins 90% of all WSG matches. I had to get 30 WSG marks to get the pretty pvp mount (which was my 50th, to get my amazingly awesome white Wyvern), and to get the first 10, it took 10 matches, to get the next 10, it took 6 matches, and it only took 4 matches to get the 3rd set of 10.
What changed? Well, I'd like to think I changed a bit, and I helped a lot. Also, having 2 druids who were awesome flag carriers helped a lot too.
How did my playstyle evolved? Well, I went from being a flag carrier, to being on defense, to finally finding my niche as a flag-carrier escort.
I did that well, and I only got better at it.
Really, a druid is the optimal flag carrier, due to forms, sprint, and all around survivability. A paladin helping out along side is amazing as well. I really think, a prot warrior is the 3rd in a trio that can really help run the flag effectively.
Hamstring. Stuns. Interrupts. Both Charge and Intercept. Shockwave.
Admittedly, I'm not a huge PVPer on my Warrior, but once I started flag-protecting in WSG, the flag carriers actually got captures more often than they normally did. I made it my goal to keep people off of our FC. Charge and Intercepting to keep up, using them as stuns to keep any melee off the FC (trying to pop a hamstring on them as you get close as well). If you get lots of people surrounding the FC, switching to battle stance, charging, and Thunder clapping followed by step-step-step, turn around and then Shockwaving everyone can give the FC plenty of time to get away.