re: Should the NFL redo how they seed for the playoffs?

There's no good way to do this and make everyone happy since each team plays less more than half of the other teams in the conference in any given year (9 out of 15 possible opponents). At least within the division everyone plays the roughly the same schedule.

For the 2018 season:

Out of 13 opponents faced, the Saints will have 10 in common with the Panthers, and they play each other twice. So, 14 of the 16 games are directly useful for evaluating their relative performance.

Out of 13 opponents faced, the Saints will have 4 in common with the Bears, and they don't play each other. So only 4 of the 16 games are directly useful for evaluating their relative performance.

It is much easier to compare success within a division vs. across it, so I think the current setup is about the best we'll do for now.