I do agree that Frosty Friend agro control is overpowered in Arcade Mode. It will be changed a bit when we do a balance pass after Tai Ming! Probably through reduced enemy priority, while buffing the survivability aspects.
However, after looking at tidbits of that run I'd say you deserve to beat the mode even with that build. Even though there's "a lot of mistakes", that's a Top #3 player performance and most people probably doesn't even come close to being able to do that with just a frosty and 2H basic attacks
In other words, I'll hold off on taking this as proof of a problematic 2H overpoweredness
(on a side note, watching this makes me look forward even more to working on the Arcade Mode mini-rework and the balance changes that will come along with it!)