I'd be interested to know what you see in the Panthers that gives you confidence in them have success moving forward. IMO, none of the NFC South teams look like they're going to have guaranteed success next year and beyond:
Saints -- Brees is another year older and their cap situation is a MESS. They can't afford anyone or anything. Defense still sucks.
Bucs -- trending in the right direction, but the arrow isn't pointing straight up by any means. Need to keep improving the defense to get back to "Bucs Football" and Jameis needs to continue to grow as an NFL QB. There's hope here, but lots of pieces are still needed.
Falcons -- probably in the best shape right now, but the big question mark is Shanahan. How will the Falcons look without him calling the plays? Furthermore, they've definitely caught lightning in a bottle this year. How will they cope with a key injury next season, something they haven't had to deal with this season. Still though, a lot of solid pieces in place and the defense is improving.
Panthers -- in dire need of OL improvement and the DL needs to play better. They stopped getting pressure on the QB, which made their secondary look way worse. Cam is still an enigma and it's unclear if he'll play like his 2015 self next season and beyond, or play like the 2016 version next season and beyond.
The Saints are fading -- they need to find the successor to Brees, and they need to find him fast. They are lucky Sean Payton didn't bolt this offseason b/c there was talk of him being interested in moving on.
The Bucs have a lot of tools, but I don't trust their front office -- they are too impatient and two losing seasons in a row, and they are off firing coaching staffs again. That is not how you win in the NFL. So, I don't trust them, for that reason. But they definitely have the talent to build upon.
Atlanta -- I hate to say it, but I agree that they have a foundation to build on. I do think this year is a fluke, but moreso on offense than defense. They are building a solid defense that is pretty young. But on offense, I do not trust them one iota -- Kyle Shanahan is about to get a HC gig (49ers, likely) and it's been reported that Shanahan and Matt Ryan butted heads all of last season and came together before this year and had a big "heart-to-heart" and really patched things up there...with him leaving, Matt Ryan is going to regress. The OL has been incredibly healthy, which is very rare. Another regression...and Matt Ryan has always been extremely erratic when his OL struggles. I see them going back down that road moving forward. Their defense should keep them in ballgames though.
The Panthers -- I see them as having longterm success b/c they have their foundation in place on both sides of the ball for years to come. The OL, RB, and Safety spots need addressing...and I believe at least two of those will be in this draft. This draft is extremely deep at RB -- I know people are fawning over L.Fornette, but I think they go with the Safety from LSU in the first round and look at James Conner (Pitt) at RB further down...he is another "Jonathan Stewart" type and fits what the Panthers like to do. Then you have OL -- simply getting healthy here will be a major upgrade. People forget they were down to their 3rd string Center by year-end. You can't win like that. But I could see this being their one weakness, and that is without being biased, in all honesty. They are building a very deep roster at many of their positions, on both sides of the ball. Some of that is through experience of players being thrown in due to injury, but so be it.
Oh -- you mentioned the DL -- they were "sneaky good" but for the wrong reasons. They were top 5 in sacks this year, but I would attribute a lot of that to the fact that the defense was on the field way too much, and I agree...they got exposed in crucial moments. You simply cannot run a 3-man rush on 3rd-and-26 and give up the first down (forget who this was against, but it stood out to me). I think this has more to do with effort than ability -- when this group came together and said it was "time to shut up and play" you could tell their production dramatically improved until get were hit with the injury bug again to Mario Addison. I think they'll be fine...they HAVE to get something, anything, out of Kony Ealy though. That dude has been a major disappointment thus far.
That help?