We have these discussion before about what doesn't work for stealth players but in that past that hasn't always caused devs to adjust their design.
If they really just don't want players sneaking for too long they could do something like
- base spot and listen DC's set by elite setting.
- every 1 second in stealth the DC goes up by 1x reaper setting
- timer and DC increase resets to base (elite setting) save DC's when you leave stealth (with normal agro check outside of stealth)
- a clear timer for how long you have been in stealth (with indicator that time is almost up)
- at 10, 15 or 20 sec (dev choice) you are removed from stealth and get agro as if you were a normal player not in stealth
- they can keep some existing design like a variable component to DC
- no other more complex increases
- all other forms of movement break stealth (wings, leap, tumble, etc) [sorry, these will inevitably break game design]
The only counter to keep track of is how long you have been in stealth. When a check is required it is adjusted by how long you have been in stealth. Players would find some places they can sneak past and find spots where they have to fight. If there happens to be some content for which stealth bypasses everything and devs feel it is becoming a problem they can adjust base DC's of that quest or increase the variable component of the quest DC's so failures can happen.
1. Simple to implement
2. Stable
3. Player stealth scores matter
4. Player choices with respect to moving in and out of stealth matter (that means again making non-detection a pre-req for assassinate)
5. Even new/undergeared players can get utility out of the design
Obviously devs will have already invested in a solution so there is no need to shoot down what you don't like with this 60-seconds-of-thought proposal. The purpose of the post is think about what works for players, what is stable design, and what keeps the server load to a minimum. A good design really doesn't need to be that complex.
Stealthy builds (assassin, etc) might have a longer max timer and faster sneak ability - limiting what non-stealth builds can do with respect to stealth mechanics and breaking the game design while still letting them utilize the stealth mechanic. Non-stealth builds would never be able to break the game for stealth players because they always have the bigger limitations.
If devs were thinking ahead these would all be scalable: (base DC, variable DC), (amount of time allowed in stealth, and the scaling factor from reaper setting) with the first two adjustable per quest and the second two applied to all quests.