Rotom is not switching into Kangaskhan. Only ghost types or pokemon with sky high HP and Defense stand any chance switching into Khan.
252+ Atk Parental Bond Mega Kangaskhan Return vs. 252 HP / 252+ Def Rotom-W: 184-217 (60.5 - 71.3%) -- guaranteed 2HKO
They don't have to be switching into Kangaskhan. Double switches, Khan knocking something out and Rotom coming in to revenge burn, Volt Turn...
You're missing my point, regardless. It's not about Khan using Facade to take out the threats that burn it. It's about the fact that if Khan switches out after being burned or you burn it with Rotom, by the time you find out Khan is using Facade you're going to lose a pokemon.
Checking Kangaskhan by burning it still means you might lose a pokemon. That's what Facade does. We've seen this argument for many pokemon last gen who ended up in ubers, but if you predict wrong with Kangaskhan, even with something as seemingly flawless an idea as burning it, you still lose a pokemon.
252+ Atk Parental Bond Mega Kangaskhan Facade (140 BP) vs. 252 HP / 252+ Def Rotom-W: 252-297 (82.8 - 97.6%) -- 62.5% chance to OHKO after Stealth Rock