Why is mesmer so unwanted in Ranked PVP?
First of all, highest personal score means nothing. I can be the highest on the scoreboard but contribute nothing to the team all the time if I want. So forget about the personal score unless you have a 500 – 500 close game.
Let’s focus on what you want to know now. It’s simple. Besides the fact that mesmer is kind of subpar, most mesmers out there are terrible peasants. They know nothing about mesmer.
The primary issue is that at very top level play the meta mesmer build (IP Shatter) is neutralized by thieves. This has translated into the erroneous perception by the masses that Mesmer is a poor choice at all levels of play and that all mesmer builds are hard countered by thieves.
Because an IP shatter mesmer wears the zerker amulet, he will also have a hard time carrying uncoordinated and clueless teams. Optimally he will rotate with another team mate and provide spike damage and boon rip, however you often find your team zerging to far and are left alone defending outnumbered in a squishy build. A guard or warrior could run in circles and maintain until his team mates got a clue, but a mesmer has a much smaller margin for error. Uncoordinated teams in ranked also negate a lot of the utility we bring through portal.
Add to this the consideration that mesmer has a fairly high skill ceiling and you are simply going to end up on pvp teams with a lot of pretty bad mesmers.
So long as you are always striving to improve, ignore the hate and play what you enjoy the best you can.