You missed Rozeboom, the 6th highest-ranked defender at 61.0 overall with an 83.5 on tackling.
I wouldn't automatically peg the bad defense on LB play. There were at least two other issues yesterday.
First, Neville Gallimore had an abysmal rating. He's in the trenches to help stop the run and he failed.
Secondly, part of the inability to stop the run is missed tackles. It's been a problem all year. We had 5 players yesterday who rated a 35.0 or worse in tackling:
Turner (30)
Verse (29.7)
Kinchens (29.8)
Young (34.3)
Durant (27.6)