I'm expecting significant improvement on D.
Every newcomer this season is known as a good defender, and have been showing it in practice.

Austin Wiley should improve leaps and bounds IMO. He's completely transformed his body in the weight room. He came in at 17 and was physically soft (literally). In the FIBA World Championship with Team USA you could see a huge difference. He looked like a straight up beast with his muscle definition and noticeably improved conditioning as well. He was slow up the court last season and looked tired a lot. He was moving very well in the FIBA tournament.
All that international experience between that tournament, and our upcoming team trip to Italy, and just being here from the start of the season will make a world of difference. You can tell how much confidence he's gained.

The two freshmen we brought in, PF Chuma Okeke, and PG Davion Mitchell are both very good on defense. I've seen Mitchell described as a "demon" on defense, and most are expecting him to take the starting spot from Harper by the time SEC play starts. And Harper was a big liability on D last season.

Got three transfers that will be able to play this season. DeSean Murray and Malik Dunbar are both known as defenders. Not sure where Murray will fit in the lineup though.

Horace Spencer and Bryce Brown are two returning that made a noticeable difference on defense when on the court. After Spencer got hurt we closed the season 2-6 and missed out on the NIT.

I expect the depth chart to shake out about like this:

C- Austin Wiley, Anfernee McLemore

PF- Horace Spencer, Chuma Okeke

SF- Danjel Purifoy, Malike Dunbar

SG- Mustapha Heron, Bryce Brown

PG- Davion Mitchell, Jared Harper

The 3 transfers, not sure where they'll all wind up because they can all play multiple positions (almost all our players can too). But you have:
F- DeSean Murray. He has the game of a PF, good on defense and rebounding, but he's only 6'3". He supposedly has the hops and strength to make up for his height. But we have 4 other guys that can play the 4 that are all the right size and more naturally talented, so he may play the 3.

Malone Dunbar is a SF/SG. I personally expect him to backup Purifoy at SF

Then Samir Doughty. Grad Transfer from VCU. He's really a SG but he's practiced at SF as well. He'll play at the 2, but he's really the fifth guard. Brown can play PG if needed, but I expect he'll be the first off the bench to spell Heron at SG

I'm very excited about this roster. Lots of talent, and as you can see a lot of depth as well which is something Auburn hasn't had in many years. Not as much experience as you'd like, but more than we've had under Pearl until now. Brown and Spencer are Juniors, but the only senior is the grad transfer Doughty, so its his first year in the program and barring injury I don't expect him to get many minutes anyway because he's essentially 3rd string.

2 years ago I would have felt very confident about making the NCAA Tournament with this roster, but as many have pointed out in this thread the SEC is loaded this season. So it will be a dogfight. We might still make it, because of the shape of the league I won't get up my hopes, but I expect no less than a high seed in the NIT.

I think OP has us pegged about right at 6th. I would say absolute best case scenario 4th place, and worst case 8th.. so 6th seems right.