Although nobody expected the defense to be this bad, I also believe the expectations were unrealistic. Much of that was based on the Patriots 2016 defensive ranking.
The 2017 NFC South is far superior than the 2016 NFC West. None of the NFCW offenses were very good, and two (Rams, Niners) were awful.
Likewise the 2017 AFC West is much better than the 2016 AFC North. Pittsburgh was the only good team from that group, and the Steelers were without their starting QB that day.
Here are the quarterbacks the Patriots faced in 2016:
Carson Palmer
Ryan Tannehill
Brock Osweiler
Tyrod Taylor
Charlie Whitehurst
Andy Dalton
Landry Jones
Tyrod Taylor
Russell Wilson
Colin Kaepernick
Ryan Fitzpatrick
Jared Goff
Joe Flacco
Trevor Siemian
Ryan Fitzpatrick
Matt Moore
Brock Osweiler
Ben Roethlisberger
Matt Ryan
In addition, consider the changes on defense. The players that ranked #4, #5, #6, #9, #12, #14 and #15 in snap counts in 2016 are either no longer on the team or have been out due to injuries. That is half of the 2016 defense!
I'm not writing this to excuse the defensive performance by the Patriots - it has been very sub-standard and is a major concern. Just wanted to point out some circumstances that make the preseason expectations for the D rather unrealistic. The belief that the Pats would have a league leading defense were dubious at best. A better forecast would have been for the middle of the pack. The issues in communication should be able to be fixed.
Unfortunately getting that accomplished prior to the next game at Tampa is doubtful. Covering Mike Evans, DeSean Jackson, Cameron Brate and the running backs would be a difficult task even if the defense was clicking on all cylinders.