I know that you are meant to be able to see in Mirkwood, but if Moria was added you would need Dwarven Tonic if you want to see. Yet in The Hobbit (Book, seeing as I will incorporate the movie) Thorin’s Company can’t see very well, yet in the mod (which I find half desirable) it is like the Movie, in that you can see even at night. So please change the sky. Northern Mirkwood should have lighter skies but still dark. Not quite as bad as Mordor at day but perfect at night. But I guess you can keep night in Mirkwood as day (mostly for gameplay purposes).
I think the forest should be denser with more canopy. That'd be the first big step in making it dark. Something like what the Twilight Forest does with its dark forest, or even something closer to vanilla roofed forests. Right now it's just... bleh. I think having a border biome of what it is now and a primary biome of super dense forest would be the way to go.
Moreover, the road should also be covered by trees, so it's harder to stay on it. The company couldn't even see where they were going besause they couldn't see the sun. Adding to this, mirkwood roads should resemble more those in lone lands and random paths should intersect with the main road, making the journey a lot harder and getting lost a lot easier
And to add, I was trekking through Mirkwood on the Elven Path and it intersects with the enchanted river at the area where it is NOT enchanted, plus there’s a bridge!? Since there is none in the Hobbit and it is not mentioned at all (if you get me) For the rest of the third age, it should probably be a lot more broken, and the waters should be enchanted in northern Mirkwood.