When his reflection changes to a young woman who needs his help, a reclusive author must enter Miraland and lead the rebellion against the crooked regime before the corruption spills into the real world.

>>>crooked regime before the corruption spills into the real world.

So what?? There are so many crooked regimes and corruption in the real world, what difference will one more make?? What is so gawdawful about the regime in the mirror world that makes it worst than anything in this world -- the worst of all possible worlds?

Alas, my impression of the logline through all the iterations is that of an interesting inciting incident, a good idea in quest of a worthy plot.? As Woody Allen said, "Good ideas are a dime a dozen: 'It's the then what?' that kills you."

more random thoughts ~

1.
Who--from Mirraland--will follow his rebellion, if they intend to overthrow the real world? Which reminds me.... What would they achieve by corrupting the real world? (Just interested...)

2.
I learned from Richiev that an Inciting incident and the Goal that it engenders, benefit from a single causality. IOW, it would be better if - as a result of her appearance (your current inciting incident) his Goal becomes to lead the rebellion (your current Goal), which isn't the case. What if your inciting incident was "When HIS reflection begs for help..."? {because What-specifically-do you wish to achieve by 'turning him against his self' (although, that sounds cool..)}

3.
...& Whatever you end up using (..his mirror self as an antagonist or protagonist), not mentioning it would be burying your hook!

4.
re-quoting Nettle: You NEED to specify the nature of 'corruption' and the threat of 'crooked regime'

Good Luck mikepedley85!

Given that your premise is interesting, it lacks clarity. You need to specify the nature of corruption and the threat of crooked regime. What will the crooked regime do that shall affect your character and the Miraland's population?