Thorn got nerfed in the lasted update 11/17/14. I find it really strange that it got nerfed since they said they were going to buff it and its not in the patch notes.
They nerfed the tic damage from Mark of the Devourer from 7 to 3 a tic in PvP. I don't remember what it used to tic for in PvE.
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They are trying to buff them. Please stand by.