Does anyone happen to have any bootleg recordings of the first few AT 2008 shows?
 

I'd like to compare her vocals before and after AT 2008 because throughout this tour her voice had drastically changed for the worse. Her singing voice has gotten a lot choppier and hoarse since then as well, as evident in the Dearest and Voyage performances of the DVD. It really intrigues me to see how much the tour has impacted her voice so it'd be wonderful if anyone can help me out here.

I don't think the tour had as much impact as the emotional impact of discovering she was deaf...

We are talking about her singing voice here. Sure, she might've gotten less confident about it and slightly more tone-deaf, but there is a pretty obvious change in the quality of her voice that was caused by her overstraining it throughout this particular tour. Speaking of her becoming deaf, the main reason AT 2008 intrigues me so much is that her deafness seemed to play a main role in her voice drastically getting worse following 2008, and this tour seems to be the start of it all. I suspect that it was because she didn't have enough time to train her voice to properly accommodate her much worsened hearing and therefore had to use extra force to sing. (The quality of her voice in CDL 2007-2008 was actually decent and not as rough and choppy as CDL 2008-2009, but she obviously couldn't hear herself to stay on key anymore.)

^I think it was a emotional issue because her hearing loss was gradual, so, she was probably performing already deaf before AT08, but as she didn't know on a official way about that, she just kept performing without giving it much thought. Once she gets the news about her hearing and digests it, she actually starts paying attention to the difficulties that were already that, and this mess her performance up.

That being said, I would say she is at the best point as a vocalist on her whole career right now.