I give the OP credit for at least suggesting that he considers KD a factor in the W/L argument. Traditional players of the objective type on forums like this usually jump all over anyone suggesting that killing is more important than capping...I know I would have at one time.
I speak as one of those objective maniacs myself. I was adopted by a group of far better players because I was just so annoying to play against; my epitaph would have been "Died trying to cap B." I usually topped the leader board with my caps and tags, but I only started regularly getting on the positive side of KDR in the last year or so. My overall Ghosts KDR is only around 1.3 (I blame clan wars), but my TDM ratio is over 1.7 and my weekly KDR nowadays is often north of 2.0. My 2.2 W/L is done with a mix of playing solo or with parties.
Playing with parties is where I draw the distinction of what I prioritize. I won't usually drop a 40 death game playing with randoms, but if there are friends in the game I will sacrifice KDR without hesitation. Continually trying to cap B solo while your random teammates are spinning and knifing each other in the corner of the map is not only pointless, but it is probably making things worse by giving them more kill streaks.
An example of my evolution of thinking was a recent (solo) game of Domination on Prison Break. We capped our home flag by the logging camp and ran to the corner with the Hummers near B. Several teammates rushed out and died instantly to the enemy who had obtained the high ground on the ridge, which should have been obvious. I hunkered down and earned my Trinity Rockets, Chopper and Helo in that corner off of enemy rushers before the other team got to 40 points. I deployed my streaks and our team triple capped and never trailed again. Finished with 36-6 with 6 caps.
While of course this is partially a chance for a cheap humble brag, but it also describes the evolution of my way of playing this game. It isn't just about getting to B first and being willing to die. You have to get into controlling areas and understanding how that influences spawns and what is going to happen next. To paraphrase Patton, "It's not about being willing to die for the B flag, it's about making the other poor SOB die for the B flag."