Strength of schedule is calculated from the opponents projected fantasy points allowed for the DEF position. The best rating is +16 which gives the player the advantage against the defense and indicates an easy opponent, the worst rating is -16 which gives the defense the advantage and indicates a tough opponent.
Rarely, if ever, are defenses picked to take one to the house as defensive touchdowns are like lightning strikes. But the Eagles defense against Matt Cassel (or whomever the Vikings play at QB) and possibly with no AP, should be expected to excel.
Juan Castillo is gone, Todd Bowles is in. As is another schematic change. The other personnel problems are still present. Will they be exacerbated by the scheme change? Probably. The off season acquisitions of Barwin and Williams were prudent. This a defense in a transitional mode and will play like one.