I bought one of these recently and it added 10 more damage to the Shield Bash(25-26 dmg instead of 15-16 dmg). I had to be in the yellow for my health and I had to be below 100% TP. The extra damage leads me to believe it generates extra hate. However I was unable to confirm if it increased the stun factor. I am satisified with the performance of the ring and it is cheap to acquire (2k on Pandy). However I believe I will run into a problem when I begin to store up TP for Spirts Within later on when I get it. Oh well I'm keeping it.
My macro is:
/equip ring2 "Guardian Ring"
/wait 1
/ja "Shield Bash" <t>
/wait 3
/equip ring2 "Verve Ring"