Yeah, with a fully modded armor and the sneak perks maxed out with full assassin set bonus, zds just stand still like wiggling manequins, they do not search for you, they don't react, most of the time not even a flinch. At times it seems like their AI is deactivated. There should be a cap to how low the detection parameter can go. 0 secs is too much. You can also avoid hordes altogether. A bit OP if we are being honest.
Edit: Of course hordes are unavoidable except when dying once. And light reduces the effectiveness of the stacked bonuses, but the fact still remains: the tier 6 assassin armor set with urban combat books and full sneak mods becomes extremely broken indoors,which is where the magic happens.