reported on us beta forums they dont stack divine purpose useless ...
my guess they will change it to reduce disarm duration.
I don't think so.
Currently as it stands you, have to spend a lot of points in retribution to get the best talents available and you barely have enough points to spend into prot to get improved hammer of justice, and while toughness seems more attractive with the 50% speed reduction it requires 5 precious talent points, having to fork out points both toughness and divine purpose would heavily gimp your PVP spec since you would sacrifice so many DPS talents that even your burst would go down, whats the point of staying close to someone in PVP if you can't damage them?
In my opinion divine purpose is fine as it is.