I'm using heartpierce and i can advise you to get it 100%, the proc refreshes plus it doesn't have any cd at all, 4 energy is in my opinion in some moments more precious then the 70 agi you'd get, for instance for me using 100% envenom buff up(altho that's tough because nit depends on combat points proc's so usually i've got 85% uptime) it definetly helps me if i don't get 4 pts until the duration ends, definetly useful.