I don't lurk here much, but I don't think anyone here has ever claimed that lethality's damage output is bad. Most people seem to have a gripe with Marksman and Engineering trees.
Huttball isn't typically a great Warzone to use as a metric for damage. Running the ball and assisting the runner tends to lower raw damage/healing numbers as a lot of time is spent running around as opposed to fighting. As noted by the scoreboard, your team lost 1-5. I wasn't there; I cannot state with absolute certainty. Perhaps the possibly geared enemy team was too busy running the ball to win the Warzone rather than deathmatching to get good raw damage scores.