thief has always been one of the strongest professions across the board (PvE, sPvP, WvW) and will most likely continue to be. thief is high-risk high-reward so that means that it’s a very skill reliant profession so while thief can be devastating like no other profession in the hands of someone that knows what their doing, it can also be very unforgiving to those who play it incompetently. the learning curve tends be noticeably steeper than most professions (especially warrior) but again, thief rewards player ability extremely well and that’s what makes it by far the most fun profession for me to play.
warrior is a much easier and forgiving profession by design but imo this lends the profession to a lower skill ceiling that makes it a less enjoyable profession to play in my eyes.
the september feature pack’s balancing changes will barely affect thief at all. the changes/nerfs are all minor and mostly fair. the only change i’m actually against is the buff to venomshare in WvW because of how stupidly strong p/d condi already is in WvW, however it might make thief more viable as support in sPvP so i’m open to it there.
warriors on the other hand got some fairly nasty nerfs all over this upcoming patch, so if anything you should be questioning warrior viability post-patch (spoiler: it wont).
