Stealth -has- a countermeasure, it’s called Detection skills. Considering you need at least 20 more stealth skills than detection skills, stealth is already disadvantaged.
If you don’t want to be spied on bring a bard or ranger or rogue with you or invest in detection, use detection spells (True Seeing, Insight, Amplify, Clairvoyance). Also True Seeing reveals every hidden or invisible creature, not just those standing next to you.
Eeeeh. I've by no means seen
every piece of gear in the game, but I'd honestly be skeptical if I even considered they were balanced as stealth vs detection. I've seen
a lot of stealth gear with very high skill numbers on it with only a few bits of detection gear with moderate numbers on it, at best.
Even worse, most of the stealth gear others have shown me have rather useful combat mods on it, whereas most of the detection gear just has... detection (usually with penalties to other things, no such penalties on stealth gear that I've seen so far...).
Factor in the fact that even without gear at all, detection vs stealth
isn't balanced to begin with (favoring stealth
a lot) and, eh...
Halved die rolls (for no good reason), stacking camouflage spells that shouldn't, invis not working right, listen being functionally worthless in most situations due to bugs. I could go on, but there's a good reason why you never detect anyone but newbies in NWN. If you're a guy with maxed out listen or spot wearing everything, I highly doubt you're even in the same ballpark as a sneaker doing the same. Factor in engine flaws and even with the same scores, you're not going to detect him.
I'm okay with a level 9 spell letting folks see you. Oozes and the like? Yes. I'm okay if Grimetrekker sees you (seriously, that class has nothing else going for it). RDDs? Uh, no. They don't get it in PnP and honestly get more than enough as is with all the bonuses (imo).
Greater Sanctuary really needs some work though. Going to the Ethereal is a big deal. It's dangerous on its own (honestly, Ravenloft's ethereal would be a nightmareland) and it's utterly useless for spying. You can't hear anything on the nearby plane but the loudest of sounds and telling one person from another is practically impossible unless they have some huge, definining trait. And yet I constantly notice people doing it to sit around spying on others all the time. Should most definitely make it so you cannot see whispers and talk channels while GS'd. Making it harder to see past 10 feet or so (aesthetically) also is more appropriate for the Border Ethereal.