Interesting taking a closer look at the numbers.
There's only been one disaster line so far this year, and it also happens to be the line that has played the most minutes - Ritchie-Tavares-Marner.
They managed only a 43xgf% together, and that was with decent 3.08xgf/60. It was their disastrous 4.08xga/60 which is the only truly awful defensive line that has played at least 10 minutes together.
The only other line with subpar defensive numbers is the Kerfoot-Kampf-Kase line at 3.29xga/60, though that of course comes with heavy defensive zone usage - and even then, they balanced that out with an equal 3.29xgf/60 on the other end.
The Engvall-Spezza-Simmonds line was also subpar defensively at 2.84xga/60, though that's not awful, and it was more than balanced out by a team best 5.01xgf/60.
The other 5 line combos with 10+ minutes are all comfortably under 2xga/60 which is excellent.
On defense, both top pairs have been poor.
Rielly-Brodie 2.81xgf/60, 2.92xga/60
Muzz-Holl 2.69xgf/60, 2.65xga/60
Given that Muzz-Holl get the tougher usage that looks worse on Rielly-Brodie tbh.
Thankfully Sandin-Dermott have been dominant out there at 4.08/1.44, though Sandin-Lilly got caved in at 0.74/2.06
Muzz-Lilly has been very good too at 1.81/1.20.