Feral Thorns

This is in responce to the thread [Suggestions] Savage Defense/Mastery Change.

Feral Thorns

Bear Form - Successful physical attacks made against the Druid recieve nature damage to the attacker. Each successful counterattack reduces physical damage taken by .50% of the druid's attack power times mastery. Stacks up to 10 times. Lasts for 5 seconds. While Feral Thorns are active, Savage Defense will not activate. Can only be used in bear and cat form. This spell will not break feral form.

Cat Form - While Feral Thorns are active, mastery no longer effects bleeds and Clearcast can not activate. Instead, increases non-periodic damage abilities by mastery. Can only be used in bear and cat form. This spel will not break feral form.

Please tell me what you guys think. I did my best to not make this over powered. I posted this in the Tank forums and didn't get any responses.

Edit: Thought of by Eightyfour and Dsanatrestk

Thank you, have a nice day.