The 'Adrenal Flow' AA is supposed to delay loss of savagery for 20 seconds after leaving combat. If you kill a mob using autoattacks it appears to work correctly , and you get an Adrenal Flow buff that lasts for 20 seconds. If you kill the mob using a combat art then you don't get the buff. From reading the details of the buff you get when it does work , it is supposed to cancel when you attack or use a combat art , presmably so it vanishes when you start the next fight. At a guess what is happening is that if you kill your target with a combat art then you get the buff for a brief moment and then immediately lose it from the art that was used to do the killing blow.
I have too seen its buggy behavior. Though i was under the impression it works if you kill with a CA, but if your pet or a advantage kills it does not apply.
For me its actually more buggy than that. I have not paid attention to what happens from what and when. But sometimes it works correctly (I asume then when I kill with a autoattack) Sometimes it dose not work at all. And sometimes my Savagery never starts to decay after combat has ended. Have 5 points in Andrenal Flow Also sometimes Savagery will start to decay during combat for me, while Im not using primals.