arp gets better the more of it you have. if you can reach 50% passively without sacrificing your crit, hit and expertise soft caps (30% in zerker, 8% and 6.5% respectively) then you want to do so. ideally youll have a grim toll or a mjollnir runestone as well, because when one of those procs with 50% passive arp then you get about 100% arp, which skyrockets your dps in a way that stacking raw str never could.
and yes, the procs are consistent enough to warrant stacking arp over strength, even over the long term. even without the procs, stacking arp to 50% or so isnt a bad idea; youll see a bigger dps increase from arp once your overall gear ilvl starts to surpass 219.