any points about viktor here are set in a folly produced by hopes that people will do stupid things. this just isn't the case.
Except that is exactly what you're doing. There is no conceivable situation in which Katarina can successfully engage on a Viktor without significantly outplaying him (and if that's the case, it's an issue of player skill).
Viktor has two ways to stop Katarina's channel and both of these abilities are usable at range. This means that even if I am forced to use one ability, I can still hold back the other to react to your play, and you can't even safely engage my allies without me stopping you.
Viktor has no channeled skills, cannot be interrupted, and you have to be in his face to have a hope of killing him. Katarina relies on having shunpo targets and exhausting all the crowd control on the enemy team so that she can channel uninterrupted. If anyone is talking about "testing champions in a perfect vacuum," it's you.