I have tested this on my SWF monk splash.
1) it procs on the extra strike in doublestrike
2) it procs on a 19-20 for PSWF
3) it bypasses deathward on mobs
4) it also works on champs with the ward (was fun erasing a stone champ loaded with defenses)
5) it works on undead--any mob, really
6) it does not work on orange & red named
I do not know if it works on reapers--will need to test
I think a great build would be 6 monk/14 paladin, or even 5/15
edit: now with vistani, you can do 6 monk centered with daggers and /whatever for a fun dagger build. Shortswords for a bit after level 12 due to AP starved (34 AP in Henshin for void strike and SCEWL/LCEWS).