Its honestly just luck of the draw, I'm Alliance too and lately I've been winning 90% of my games, won 90% of my WSG, every AB, most of my EOTS (70%), and all of my AV (2/2 matches).
You have to play your best, you will be surprised how much a single players decision effect the game.
Even though defending bores me.... I'm good at it, and I'm good at snagging/defending bases solo as a rogue, its my job to be annoying and get objectives like that, even though I might not fight anyone for 5 minutes at a time, it really guarantees a free base and sure victory, lightening the load for the rest of my team to apply pressure and be elsewhere, thus putting my win % up, I try to be as productive as I can.
Always be productive, don't lurk around a big group of hordies you know you can't beat, take an objective, walk away, do something.
The thing I enjoy about team games is that its like a game of chess with so much possibilities and counter play, no one has the advantage there is ALWAYS a way to win, communication is key. Even if you can't kill them 1v1 you can take objectives and have better teamwork/communication to take the win.
It really is the little things that count:
Gear: I didn't play a single BG when I came back to WoW until I got the BiS gear for WoD (PvE and PvP gear) and found my style (choose my right spec/talents), I didn't want to be an under geared burden on my team, I also spend a couple days farming mats before I started to BG too (have 800 weight stones and other alchemist goodies).
Communication: just little things go a long way, I tend to tell my teammates to /go and /luck as I assure them that I can cover the base well, also call things if you see them first, like inc (incoming) stables or flag room or whatever it is, call the hordes location/headed direction before you team sees them/realizes.
Map awareness/Pressure: Don't just follow enemies like a zombie and try to get honorable kills.... then get killed, lurking around mid or just fighting is for arenas, in BG's there are objectives and therefore you will need to know when to fight to win, don't fight and burn your cooldowns if you don't have to or if there is something better you could do. know when/where to be useful.
Positivity: As corny as it sounds, positivity goes along way, don't be negative, apologize for your mistakes, know when your wrong and learn, don't always be so quick to blame others. When I have people on my team crying and raging it already feels like a loss and thus effects the teamplay/gameplay.
I could talk on this issue longer and in more precise detail BUT if I did, I would just make it an actual thread to help others.
The thing I like about WoD is that you don't feel helpless as an F2P, its quiet balanced in our bracket, so long as everyone knows their roles/strengths/weaknesses a win can go either way.
I'm not saying your a toxic player, but its not good to be self entitled, you don't deserve a win, you have to earn it.
I learnt alot about teamgames/teamplay because I was playing LoL for the past 1.5 years and I got myself a high win % (support role, diamond 2), there's just things you learn, my skill definitely transferred into WoW and improved me, I used to be a 1v1 rogue brawler until I realized how much a rogue can impact the game when playing to win.