Heartbreaking node decreases dps

Taking the Heartbreaking node on the passiveskilltree shows a decrease of DPS in every attack while taking other nodes with "increased critical damage bonus" increases the DPS displayed.

Works as expected with bow damage of ranger, but i dont know how an increase of strength and critical damage bonus could decrease the DPS of a quarterstaff acolythe of chayula monk.

Edit: it is the strength which makes the DPS shown decrease but i dont know why.

Edit2: I now Know why, strength made me gain or loose hp and thus fall in or out of full Hp damage boost.