After reading through maybe 8 pages from the start, I'm just...gonna chime in with my somewhat limited experience.
Besides GW2 I've played WoW, Rift, FFXIV and ESO, which have stealth classes.
ANet's implementation of stealth, and by extension invisibility, is problematic. So here's a (likely unwanted) list of comparisons:
GW2: stealth/invis broken by dealing direct damage (Anyone remember permastealth trapper?). FFXIV/Rift/WoW: stealth broken by taking damage or initiating an attack. ESO: it lasts 3 seconds and requires a resource to use, breaks on doing damage or taking direct damage.
GW2: cannot cancel attacks easily, auto attack is notoriously annoying to stop and often attacks will fire whenever you use a skill with an enemy targeted. Next 3 games: Stealth/invisibility shut off auto attack. ESO: There is no auto attack, it's all manual.
GW2: some sources of stealth or invisibility are instant and do not stop auto attack (midnight signet for example).
GW2: stealth is something you can permanently upkeep out of combat. Other 4: Same thing.
GW2: stealth is something you can permanently upkeep in combat. next 3: no. in the first 2, you do however have skills that let you re-enter stealth on a long cooldown. ESO: It costs a resource which has significantly lower regeneration in combat and thus cannot be kept up without sacrificing something.
WoW/Rift: you have a window where you can't be revealed in the form of those long cooldown re-stealth abilities. ESO: You can just re-stealth right after. GW2: Hahahahahahah sorry were you trying to stealth? That shot that went off on its own half a second ago just broke it and got you revealed. (Turn off auto-attack, noob)
Of course, I also saw mention of issues in Shadow Arts, and saw someone's comment that kinda struck home: What about specter? They have a trait that grants barrier to the target when you apply stealth...but it requires stealth to expire before it will trigger on the target again. Why aren't more traits like this? They could re-budget the traits around applying only when you first enter stealth, or when Revealed expires, stuff that requires more interactive gameplay.
So...what I'd like to see changed:
SA becomes more interactive, kind of like what ANet threw at Deadeye in its rework. (mesmer's prismatic understanding could use that, too, I guess)
Invisibility and stealth traits that periodically apply effects instead only apply when applied to a target that didn't already have the effect (and are rebalanced around that).
All stealth/invisibility effects to grant immunity to being cancelled (but not remove Revealed!) for maybe 2-3s, when first applied, following the prior mentioned condition.
"you tried to hit something, you're revealed now" outside of above immunity window.
more classes get reveals. some reveals (new and old) are unblockable/undodgeable/AOE as is thematically appropriate.
All this said, my expectation from ANet: Nothing about thief changes meaningfully. people continue to scream into a vacuum like it has some meaning. Guardian gets buffed and elementalist gets nerfed (again.)