It never has worked. It never felt like it worked. So I tested it out in world builder:
20 warriors with shadowwalk vs 20 warriors on a forested hill
results:
3 wounded attacking warriors left.
Bah! I knew it didn't work! I knew it felt highly unlucky that I seemed to lose even the not so close ones.

20 warriors with shadowwalk vs 20 warriors on a forested hill
results:
3 wounded attacking warriors left.
Bah! I knew it didn't work! I knew it felt highly unlucky that I seemed to lose even the not so close ones.
