Game Mechanics: Dark Reaver proc - not transfering to character

[Kelven]

Having recently acquired a Dark Reaver, I've noticed the proc doesn't transfer the strength it steals to the shadowknight.
**Steal Strength **
Description:
1: Decrease STR by 15 (L1) to 27 (L48)
Recourse Effect: Steal Strength
1: Increase STR by 15 (L1) to 27 (L48)

With no buffs on, waiting for the sword to proc - I get a " target weakens " message, telling me it is effecting the mob. But no increase in strength , or buff icon.

With Siphon strength active - I get the "target weakens " message, and a message telling me it has overwritten Siphon strength with Steal Strength - but no increase in strength over the original 10 from Siphon Strength.
The buff name then changes from Siphon Strength, to Siphon Strength Recourse.

After letting that fade, and letting the sword proc again, still no strength is transferred to the shadowknight. I've asked a couple other shadowknights and they too receive no buff from the Dark Reaver.