I have really enjoyed the Miz, and I would call myself a fan, but to be honest I think Truth entirely owershadowed him in Awesome Truth. His chemistry with Riley was much better for him.
Miz seemed out of place during their entrance, and his parts of the promos were more awkward. In ring it was close imo, but for example in the Cena/Rock match Truth was much more electrifying.
Once the conspiracy side of the story died down, Miz's character suffered for not attacking Truth earlier, imo, although having the titles could have changed this.
I kind of agree with you on that. Truth did overshadow Miz. They came out to Truth's music and Truth was allowed to keep his same character while Miz was forced to make changes to his, although past beatdowns on Cena and Riley proved that Miz was capable of playing crazy to an extent.
The problem was that Miz/Truth were paired solely for the conspiracy storyline to keep both of them relevant after Cena moved on to Punk and Riley moved on to feuding with Vickie's boys. Once they had feuded with everyone they felt had been overshadowing them (HHH/Punk/Cena/Rock), there wasn't really much left for them to do.
From a character perspective, it would've made more sense for Truth to be the one to turn on Miz. With all of Truth's talk about conspiracies, he should have attacked the D-Lister media whore in a jealous rage. Even if Truth were the one being Wellness'd, he could've just hit his finisher on Miz, said "I'm done with you" and walked off into the sunset for 30 days, and his "punishment" could be putting Miz over as a face (the same way that Morrison put over heel Truth).
And like you said, Riley and Miz's chemistry was a bit better. And Truth returning as a heel could've been used to rebuild Riley (although Truth would still be too high up to job to the kid) and facilitate a Miz/Riley reunion as faces.