I am very badly affected by a huge FPS drop at the watch. I cannot progress at all, I need 100 x T4 essence to buy the crafting station I need to get to the Ascended realms and I certainly am not going to run a vault, with the combat that would entail at 7 FPS.
My PC is well above your recommended specification, and I have confirmed that this FPS drop does not occur on my main character in online mode.
Update: Someone in Discord suggested a way to rectify this issue. I logged out of the game, logged back in and returned to the Watch - no FPS drop this time. Progress has resumed.