I am not sure this appears everywhere, since I had not time yet to check this in original Hexen maps. But (on my maps) I've noticed many times that Stalker Leaders (shooting ones) shoot in player's direction even if he is beyond wall and cannot be seen.

It does this in original Hexen.

The bishopds do this too in the original game <!-- s:) --><img src="{SMILIES_PATH}/icon_smile.gif" alt=":)" title="Smile" /><!-- s:) -->.