When you attack an opponent being in stealth it is cool that they dont magically know where you are and combat you directly. But that way you could attack them in stealth over and over while they just stand still doing nothing against you.
In my eyes - enemies that are attacked by stealth players should begin to slowly roam the area and search for threats.
This is a Video Example of such an Stealth Attack (After the first kill I go out of stealth with gale, and you can see suddenly the enemy begins to run / attack the player):
https://www.twitch.tv/videos/773513831
. Still some mobs do react trying to search for player but some mobs, especially ones in buildings/dungeons just get stuck.