Nightfall final impossible with scorch

Do you mean that you took only Scorch to r9 to try the last tier and expected it to work?

The event says you need an r9 clone to enter the event, but they did not say it would be doable - And while I am typically a proponent of "most players do not interact with information outside of the game to always know what other players know," the reality is that you are posting on this forum right now.

. . .We've known it was impossible with just Appo, but that Appo and CX-2 could do it.

They made it pretty clear the event was tuned to 4 r9 characters, though it was possible with just 2.