Rengar doesn't need a rework. He just needs his numbers moved around a bit. Reworks are only if the kit isn't useful or fitting, and rengar's kit definitely works and it certainly fits. He still gets used in the OGN from time to time, so if koreans still see him as useful, then he probably has his niche somewhere. Heck, a team in the OGN did support morde once.
And why bother doing sotd yi when you can do sotd rengar? Ult, jump, super q, regular q, dead. Build IE for maximum lulz. adc forced to get armor before other items.
No seriously, sotd + IE means instant death for any squishy champion without armor. Combined with the high ad steroid that rango's q has, plus the ability to crit, this can mean 1250 damage on the first q before armor reduction. Followed up by a 700 damage q, followed up by a 500 damage aa.
So 2500 damage just barely over a second. Before any armor calculations. And most people already run some flat and % armor pen. And the average adc, with no buffs, will have about 40-60 armor at late mid game. Basic defensive bruiser will have 10 flat armor pen and 8% armor pen through just runes and masteries. So they will basically only be fighting you with between 27-45 armor. That's about 30-5% reduction. That's still 1625-1750 damage in a little over a second. If that didn't kill them, you still have your e and w and aas to top it off.
It's taking rango as an assassin to the extreme. They will need to itemize against you in some way, or they will ALWAYS fight with one champ down.
I don't know if you have ever played Magic: The Gathering, but this kind of build reminds me of the type of player in that community known as the Timmy. It is terrifying if you manage to survive or win lane while rushing that item, but most of the time your lane opponent will just out-brawl you whenever you show your face. I'd probably go for Youmuu's Ghostblade instead of SotD, they do similar things but YG builds from Brutalizer.