Seattle is for real, imo. They could upgrade their WRs some, and maybe some other areas, but they are real solid.
So much of this league is momentum. It also helps to have a decent QB. Arizona has both of those things going fully against them right now. It's a bit like the Cowboys before Wade got axed. The team was not nearly that bad--recall they were getting stomped by so-so teams in the end--but they had thrown in the towel.