Since Update 13, I've noticed that everything seems more aggressive.
Imperial sewers - some bosses will aggro the first step into a room, even if you are hiding on the opposite end (no where near the blue circle).
Thieving - hidden, eye fully closed, no NPC near you, yet get a bounty for stealing (also being "noticed" when no NPC, animals or other visible forms of life are in the house)
Mobs - chasing far outside their boundaries, watched some dreugh chase a guy inside Wayrest yesterday. Also aggroing at greater distances.
Was this a planned change I missed? Otherwise, definitely a bug. I'm not playing IC until the boss thing is fixed.