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.
Let's imagine that we have 2 bis rogues(2 t10 items). with 2 diffrent combat specs
1 spec is full evic (with 3tals in evi and 2tals in ruthlessness)
2nd spec is 'low rupture' (with 3 tlas in evi and 2 tals in Blood Spatter and 0 tals in ruthlessness)
Which one do more dmg in icc 25hc? Is it worth it to use low rupture(we use evic+rupture in that way) spec for little bit more dmg than only evis one?