The mysterious atlas leak. I have read up on the issue as I have one as well. Seems there are several possible leak points. If it is a truly large amount of oil gone I would look at the seal between the transfer case and transmission. I have also heard of them burping some but not as much as you describe. When I talked to Atlas they said that is very uncommon as I asked them many questions about leaks.
I finally pinpointed mine to a very small leak (you can see the drop of oil bottom left on the transfer case). I called Atlas and they sent me out 2 seals to replace the existing seals. I took the part out and replaced the seals and it stopped almost all of it. Now it is so minimal it is not worth watching. It wasn't that much to begin with. Yours sounds like a lot more than mine ever was.
You can see the oil is down a little on the site tube after 5000 miles so I am talking a very small leak! Took me awhile to pinpoint it. Mine leaked from the circle in the middle of the pic with the black screw holding it in. Good luck diagnosing it and write up what you find.