Ive tried out the frost staff taunt on my mag dk and while it does work I think its very underwhelming and difficult to use. I have some suggestions.
1) reduce the frost staff heavy attack cycle time by 40%-50%, with a corresponding damage reduction of 50% and shield improvement by 20%.
2) or get rid of the shield altogether and give it a 25-50% chance to root/immobilize instead.
I believe that's all that's required to make it a viable alternative to the undaunted taunt. The way this weapon is set up now it can (should) only really be used for tanking, and thus should do less dmg and have more useful utility.