Right now 65 attack is the most op build due to the leaf-bladed axe being better than the whip (for pures and zerks)
as for prayer, go 31 if all you want is edgeville, 45 if you just like nh hybridding, 52 for smite or 55 for spirit shield (not recommended for zerker tbh, but cool to have for clanning/ being a completionist). 15 prayer is OK I guess but if the enemy chooses to use smite then you're shit outa luck. have fun spamming ppots instead of food. Plus you only have the option to either go unskulled or 60 attack and risk the scimmy.
yeah yeah, ags is op, but you know what is more op? zgs to gmaul or leaf axe to gmaul. zerkers still have low enough def for gmaul to be really op. Its just that a 50 attack build doesnt really work very well due to generally low accuracy.