Getting ARP capped is what you should aim, but only when other stats are capped. Get 26/26 expertise and 17% hit cap (5% from talents + 3% from raid + 9% from gear). You dont want only your attacks to hit, you also want your poisons to not miss too. After that, you can go gem ARP + use arp food. But dont use arp flask too. Use normal AP flask.