I was playing Warwick and noticed that I couldn't see 50%< Kha'Zix when he used Void Assult. I haven't checked to see if this is a problem with Rengar yet but that needs to be fixed since they are in a stealth state.

Blood Scent has never (intentionally) revealed stealthed champions. It is intended to give you the movement speed bonus, but NOT reveal stealth.

No it was intended to be as it stated to see and track anyone below the hp threshold including stealth. A long time ago the counter to stealth was Warwick.