Re-read that post again. I explicitly stated "The only times that you won't want to use Onslaught are when it costs you a usage of Inner Chaos (which is going to be tied to your Infuriate uses anyways), or if it costs you a use of Upheaval (maybe don't do that)."

The gauge from IC always tied to Infuriate. There are no "natural" ICs. So you can temporarily borrow from this gauge and use it on something else (incurring a loss if you aren't able to pay it back in time), but you're meant to spend that gauge on IC before Nascant Chaos runs out.

So no, I don't need to do the math on something so obvious. Onslaught on average is small gain over natural FCs. Gauge from Infuriate should go towards IC. All the potency numbers seem to be adjusted to make gameplay more forgiving now, so long as you remember to hit your combo. Fell Cleave is really just there to prevent overflow gauge. You can try to min max an extra 10-20 potency if you like by messing around with Onslaught, but remember that your standard combo is 293 potency per GCD on average. You'll see even less variation between "good" and "average" this time around.