I like randomness to an extent, accounting for NPCs' spontaneous decisions is a welcome part of the challenge for me, so long as there's enough of a window of predictability for the player to work with without having to rely on favorable RNG. NPCs in Dishonored for example often don't have fixed patrol paths, but you can generally expect them to reach a logical point in their walk before deciding what to do next, if they take out a cigarette, you can expect them to just stand there facing their current direction for a while, etc.
With the head turning here, though, often there's little a player who's aware of that behavior can do if being in complete darkness is not an option, as in the training room I mentioned above.