I started a thread on PCF about the Pet Focus - Decrease Regeneration passive buff and based on the replies, no one has any idea how to get the criteria moving from 0.0%. So I filed a support case as well.... it take a few months to get an answer based recent response times though.
My Leprechaun has reached level 11 and in spite of taming a few bunnies on Calypso, the criteria remains at 0.0%. When I put the required number of essence in carried inventory, it changes from red.
I've unlocked both buffs on a Sapphire Devil, so it isn't my first time, not that it's...