Diminishing returns on stealth.

So why is there no diminishing returns on stealth in this game? Perma stealth seems like a pretty boring/broken mechanic.

I'm not sure it's broken. Attacking breaks stealth. And if you land a hit on an enemy you are revealed (in addition to other circumstances), meaning you can't re-stealth unless you have something to remove revealed. I believe only deadeye can do that, and if they're staying permastealthed they aren't doing damage, lowering their overall effectiveness.

That being said, a thief or mesmer who has 30 seconds of stealth is annoying to deal with if not for the sake of hunting them down in PVP settings. Otherwise permastealth is trolly, but kinda useless in most circumstances. Can you provide an example where it is broken?