There's a number of things wrong with the Saints this year, defense in particular. Someone was showing Ryan's defense's rankings, and interestingly, none of them were ever top rated, as a matter of fact, most times they were either middle of the pack or below average, so I'm confused on how he got this label as a defensive guru.
You make a good point about the lack of corners/secondary, because at the start of the season, on paper, the Saints appeared to have arguably the best safety tandem in Vaccarro/Byrd. Keenan Lewis is in my opinion a top 10 corner in the league. After him though, every other corner is average or worse.
You really have to ask though, is it the DC or is it Payton? How many DC's is he going to have a tumultuous relationship with then end up firing?