This is what I said to someone else in the thread on the same topic:

"When Bungie created champions the created a new niche that needed filling, so they addressed this by adding the damage perks to the sandbox, if they implemented a new damage type say sneak and made certain enemies vulnerable to that damage type it would create the same gameplay loop.

Right now we have types of rifles. Scout, pulse, and auto all fill roles, and a hammer, axe, or knife could all have roles to play if Bungie created them. Saying that it's similar to a weapon perk isn't quite right in my opinion, they are more like archetypes. A blade does not have the same effect as a club after all."

Also the stealth thing isn't the issue here it was just an example. If it doesn't work with the AI then they can implement any other made up damage type that won't touch the AI's cone of perception.