it would seem killer physique stop working at some point.
when i had the run as a simple warrior i never had this problem but since taking berserker, sometimes it does not work anymore in my runs and my health regen does not increase.
my skills bonuses are :
war cry : second wind lvl 2
warrior's constitution : combat training lvl1, toughness lvl 1, mighty strenght lvl 1
killing spree: killer physique lvl max,dauntless lvl 1
leap: trembling impact lvl 1
rage : none