Whenever I play ADC now I like to contemplate between Shiv, PD and Runaan. Shiv burst is better late game, PD is great for surviving and Runaan if you wanna dish a lot of consistent damage. In the case of Jinx, I'd better stick to Shiv. Also to be honest RFC is quite underwhelming for me.
Essence Reaver tho. I build it on Sivir and shenanigans ensue. W downtime on 2 seconds, Q up often, can ult every fight and spell shield is now used as a safety tool, not a mana refill tool. I lost as Sivir twice tho and one of them was because Cowsep Style AP Yi rekt my team.
FYI, Cowsep AP Yi is (excluding boots), Devourer, Guinsoo, Hextech and 2 more items. I'd put Zhonya and Nashor in it, although Lich Bane is good too. The result is Yi with roughly the same damage that deals 3 types of damage at once that heals better and have more consistent damage, compared to Regular Crit Yi.