Some advices.
Well,
PvP balance is actually not that bad right now. Each class has builds, which work well in certain situations and against other classes/builds. There is no ultimate “i win” button. Some builds just require more practice than others.
Right now the most stable 1v1 class without a doubt however is Mesmer. Its easy to build a mesmer with a lot of defensive capabilities without having to give up much. You can get away with a lot of mistakes thanks to evasions/stealth. Also you have the strongest 1v1 ultimate = Moa.
Lot of well executed builds can go head to head against mesmers in 1v1 and have a chance…until they get moa’d for 10 sec.
If you don’t like mesmers, then thieves are quite decent. They have a lot of cheesy builds, but they can be effective. You may try to keep your eye on unicorn thief (http://www.gw2db.com/skill-builds/985-lowells-unicorn-build). I used to run similar build (with different utilities though) I used to be able to win 1v1-s pretty decently even without much of experience.
But my best advice is to just pick a class you like and try start trying to theory craft yourself. Keep playing and modifying the build by your own play style. Meta game will always change, so there will not be a ever lasting best build out there, just get comfortable with a class you enjoy playing.
Talve / Mesmer
Seafarer’s Rest
Good thiefs would dominate 1v1 most likely if they can keep themselves from being hit fake attack the invulnerability, prepare for the real backstab, game. However they wouldn’t be able to kill everything a good guardian could probably kill them same goes for everything else. You can also use block skills if you know the backstab is coming there’es ways around it. And yes there is a such thing as good thiefs no matter the build they are running.
It needs to be something like a 5v5 where you have people preventing and healing over the damage so its not as bad or noticeable and its even team fighting with fighting as the objective.
(edited by R E F L H E X.8413)