I would like to start this by saying I've been playing GW2 since launch. I used to play PvP back in the hotjoin days before AT's, and Ranked PvP were a thing. I'm a rank 560 in PvP and have played a total of 15,438 games across all of my characters and 10,079 of those were played on my thief. I've never felt like PvP was as broken before as it is now, and I have also never felt like I should make a post on the Guild Wars 2 Forums until now.
During my time on Guild Wars, I've taken a few breaks but I can firmly say that I remember the days when thief was the #1 1v1 class. Seeing as how thief has always had the highest learning curve, it only makes sense that the most complicated class to play would be the best at fighting 1v1s. That point still survives to this day as thief remains the hardest profession to play (aside from gimmick builds that occasionally pop up through profession exploits that also occur on other professions.) Over time the power creep has set in well for other classes while leading to the decline in play for other classes. Over just the past few months, ranger is the prime example as there was never a prime balance patch where they went from the red headed stepchild to the families golden child; over time they had a bunch of smaller positive changes that really helped progress the professions damage, sustain, and popularity. The opposite can be said about thief, the class that 5 years ago was the best class to 1v1 on. A very long series of balance patches have forced thieves into a pvp class that has been pigeonholed into the sole purpose of decapping and +1-ing fights. While there's nothing wrong with this particular role, it is shameful that no other class has been pushed this far into a single monotonous role. Going through each of the nine classes:
None of these other classes have been pigeonholed into the same constraints that Thief has. As a top 250 PvP player I have seen nearly all of the thief meta builds, and the glory days were when you could 1v1 or (before this current balance patch) simply do damage. The current big problem with thief is obviously
A: the damage is absolutely terrible and you cannot win any 1v1s. Before this balance patch thieves struggled with winning 1v1s because the profession has been on a steady decline in every category possible aside from mobility while every other profession has received plentiful buffs in damage and sustainability.
B: A majority of initiative a thief uses is spent on defensive purposes as opposed to offensive purposes. Defensive purposes would include going into stealth. Black Powder Shot alone costs 6 initiative to use and that doesn't include the Heartseeker, Bound, or Cluster Bomb that the thief is also forced to use to finish going into stealth. With the current playing style for everybody unfortunately being low damage and tanky builds, initiative is a big problem for thieves as we're forced into extended fights where the thief inevitably doesn't do enough upfront damage to kill the person and so the fight drags on until the thief inevitably runs out of initiative and dies of attrition. Hence where thieves are forced into the +1 nature that no other class has been forced into because they're more properly balanced.
The "High Risk, High Reward" motto that was originally used for thieves has become a sham as even using a berserker amulet, auto-attacks do about 300-500 damage each. Backstab does less than 5000 damage and that's for D/P: one of the thieve's most offensively powerful weapon sets. However thieves are one of the easiest classes to kill due to having only 1 skill that supplies stability for a single second coupled with a low health pool and no extra toughness. Core necro is just one example of a class that can keep thief fear-locked for an eternity as the thief's health quickly dwindles away from other conditions. Power rangers, mainly power soulbeasts are melting thieves in a split second with nothing to save them. Guardians and elementalists can simply burn them to death. Engineers win the battle of attrition. Mesmer and some warrior builds are the only two professions that thief has a feasible chance against. Not to mention that that is only sometimes with warrior.
I'll try to keep this short, but in short: The thief that was born into Guild Wars 2 has died. The best 1v1 class with the highest skill floor and ceiling was wasted.