I still don't understand why anyone should care about losing a stock or two to RNG if Hero isn't consistently winning matches because of it.
The fact that its happening at all is enough indication that upsets that are completely unearned are very possible. This is what should be being discussed, and "but it hasn't happened yet" isn't a refutation of the mechanics in question.
One scene banning it quickly doesn't say much on the grand scheme, but even GimR is undecided.