Actually, I posted something about this. I've seen it with WUR with counterstrike talismans. Also seen Sentinel Mayan Priestess revenging when she was targeted.
The specific cases appear to be:
1) WUR with counterstrike. Use a single target hitter to hit one of his allies and do enough damage that he takes damage and he then attacks as though he was hit directly.
2) Use a single target hitter to hit Sentinel Mayan Priestess. Do enough damage that it transfers to the blocker on the defense and she then revenges as though the other toon was attacked.
I believe the revenge also happens sometimes with DoT effects, not certain about the WUR. So both counterstrike and revenge appear to be bugged, unless this is the way it's meant to work.