This was an era within this division that Bud Grant's Vikings became mediocre while, basically, the rest of the division remained mediocre as well. Until Ditka's Bears assumed control, that is!
Each winning ten games as opposed to nine, I guess you can call the '79 Bucs & Bears both better than mediocre. But really not by much. Tampa Bay at least now had a semblance of an offense to go with that D, but that 5-0/last-unbeaten-team start aside, their regular season campaign was not all that impressive. The very next week they lose to the 0-5 Giants! And then get plastered at home vs New Orleans, 42-14! They bounce back, going 4-1 from there, but against all losing teams. And then the season-ending skid which maybe (maybe) a monsoon helped put to an end to in the finale, thus TB sliding in as division champs. Yes, they beat the Eagles and go to the NFCC - yes, massive accomplishment - but I always felt that Chicago (who really should have beaten Philly as well) was the stronger of the two if I had to pick. Bears did have a tougher schedule.
If strike-shortened 1982 is enough of a sample-size, I may pick the '82 Bucs as #1 in this exercise. They start 0-3, give Dallas at Dallas a good game as they also did at Min and vs Wash. And then starting with a win over Miami in Week #4, they end things on a 5-1 note and give Cowboys another good game on the road. Extremely likely, to me, that they win at least 10 games (I'll lean toward 11) had '82 gone full. #2 if you want to include ’82? How about the Pack? A strong-second they’d be IMO.
Now if '82 isn't enough a sample-size? Then I'll give it to the '78 Vikings. Better than '79 TB/Chi, and noticably better than any of the 9-7 division winners that would follow. Yes, they slid into the playoffs - and got HAMMERED in LA - but Tarkenton and plenty of that crew were still around. They still showed signs that season of what they were most of the decade. Quality-wins vs Denver, Green Bay (and then, later, a tie), at Dallas, and Vermeil's playoff-bound Eagles definitely a must-mention!