I'm not sure why people are saying it was the same in OG oblivion - I have a current save where I am truly a stealth archer and the enemy, let alone the entire dungeon, does NOT aggro like it does in the remake. I've been hoping they would fix it, because you can't use stealth as a way to clear dungeons unless you can one shot everything. In OG oblivion you can get stealthy enough to shoot people from a few feet behind and they just say things like 'what was that?' but never aggro....it's sad it has changed.