I would wait to hear from one of the second year students about rotations. As a first year, I know nothing but rumors, and those stink. I know this isn't for sure (so I guess this is technically a rumor, but it is fairly solid info...) I'm pretty sure that UTMC - Knoxville made an offer to our school for us to be able to do CORE rotations there, but the offer had to be refused because it was unfair to our students (it cost way more per student than should normally be charged, they would require our students to take the USMLE boards as well as the COMLEX (which you are required to take as an osteopathic student, etc.) UTMC - Knoxville is also looking down the road when the med school in Memphis is going to have to enlarge their classes, so they can't take a whole bunch of students from DCOM now just to say no later. It's kind of a catch 22 for them. HOWEVER... as a third and fourth year student, you can do as many elective and selective roations as you want there, and those are good times to get to know some of the program directors and residents if you wanted to do a residency there. Plus, they might change their minds... you never know.
As to core rotation sites, Knoxville is hospital-saturated. There are 4-5 hospitals for sure that are great hospitals, places I would go to if I needed something done (in fact, I get to test that out here after 1st semester when I have my ACL reconstructed). The doctors are great at each of them, and they will be great teachers.
I'm not sure about Erlanger in Chattanooga. I know they have a relationship with UT - Memphis, but I'm pretty sure they have signed onto our students coming for both CORE and selectives, electives.
Don't worry about the third and fourth year rotations. Our Associate Clinical Dean, Dr. Lenz, is doing a great job and will make sure everybody has a great place to go. Focus on getting in for now... that's the hardest part.