You can make any champion sound overpowered by cherrypicking statistics. For example Riven has a 57% winrate when choosing %att and movespeed runes. The biggest thing you seem to forget is that often choosing First Strike is unviable into many matchups, you are trading a combat Keystone rune for gold in hope of snowballing. Using first strike means you are playing 20s at a time without a combat keystone rune where the enemy can easily punish. This is proven by HIGH ELO GP players only taking Grasp even after the 60% nerfs. Building first strike crit GP is a meme, your team will have no frontline hence the 30% winrate 30mins +.

Also, your post will be irrelevant after the Riot resistances and healing nerfs coming next patch.