I don't want to impose on super high level pro jp onry SBO winning ideals, but when changing the fundamentals to better suit an even match up, like a mirror, it goes without saying that both characters will need to make that adjustment, since this character is very good at capitalizing on their own weaknesses, similar to Tager mirrors where Tager can easily Anti air another Tager. The factors that come in here, that being luck, gimmicks, etc etc, are not dependent, crucial, nor exclusive to the match up, the main detail about match ups are character traits and strategies, things like gimmicks, ticks, yomi, buppa, etc are player factors, independent from match ups.
If Hima loses in Arakune mirrors, that means that Hima is bad at Arakune mirrors and doesn't know how to approach the match up, not that the match up is 7-3 or something like that, Hima would have to consider a change in strategy and approach, work on his footsies, etc. It may be a tedious up hill fight, but it's like that for both players, at perfect play.
And match ups assumes perfect play, or at the very least that the players in question are of equal skill with their respective characters. The trick with mirrors is to understand how well can Ragna capitalize on Ragna's weaknesses, being average mix up, easy to DP/barrier block strings, low health, etc. With that is mind, it's natural, like any match up, to assume a specific strategy. Gimmicks, luck and all that are considered after the fact, and by the player, not the character.
I'll admit that I understand the concept that Jin vs Jin will feel and play out differently than say.....Jin vs Lambda, but that's in the same respect that Jin vs Bang will feel and play out differently than Jin vs Ragna.
Different character to fight, different strategies applied, and similarly, if you don't know the match up, you're gonna lose.
That's just my view on things.
*strolls off*