Quote Originally Posted by Wulfgang View Post
It occurs when you critical on a Regen cast. The potency of that Regen is higher than a non-crit Regen cast afterwards; as such, you get the "No effect" message when trying to overwrite / extend the duration.

Quick question, haven't verified myself but will this effect work like DS/Conv/etc with wrath stacks to boot? Honestly, I don't see many warriors these days, but that could be another reason.