I can certainly agree...many times, like the Saints, they will make themselves one-dimensional. Lets be honest though, considering what happened in Dallas last year, their defense was pretty porous. If the current Dallas team had played them, they would have gotten whacked...straight up!
The combination of Miller and Ware, if they can both avoid wearing down toward the end (real possibility), gives them an edge that they did not have last year. The destruction of the injury-depleted 49ers was rather foreboding for the future, even considering the circumstances...Manning was playing pitch and catch...it could have been much worse.
Finally, it was Seattle's vaunted secondary that had a hand in said collapse of the Denver offense. It happened again this year in Seattle. Dallas simply does not have a secondary that is comparable. Yes, they play hard, disciplined and inspired football, but they will need to become MUCH better for a possible meeting with Denver. Eli had 3 TD's and was largely unfettered last week...that should be concerning because the older Manning has an even sharper knife. Dallas can certainly play keep away, but I don't know if that would be enough...I really just don't know.
I would also add that the Giants defenses of 2007 and 2011 (SBowl years) each had around 50 sacks for the season (52/48 respectively)...they were that disruptive and it was the biggest reason why they were able to derail the Patriots both times.