Quick Question on Duskblade

So, I was thinking (dangerous, I know, but riot doesn't seem to be so someone has to). At the point that nightfall is an on hit effect, doesn't that mean if let's say I'm playing Jax, that I can aa a minion, jump to my enemy, cast my w, and then because of sated devourer get nightfall twice? And would that not more or less be a one shot? What about Rengar? Sure, normally you build warrior on him, but if you get double zed ult just for RIGHT CLICKING the enemy, why not build devourer? And why not one shot the opposing adc and end a teamfight in seconds? Riot, I get it. You want to have those dank assassins back in the rotation. But this... this is just such a shit show. It's gonna be like release Rek'Sai except EVERY ASSASSIN(and why not fighters, I'm sure Yas would just love this, since you just spam e to your lane opponent and then q them for the nightfall) will be rekting everything. I understand you want faster games, but this... %missing health damage? You must really hate tanks. You're doing this wrong I promise.