It's been said, but the best way this has been combatted in the past is by blowing up the man setting the pick. The refs are going to have to start calling it to protect the WR's. This is how Seattle shut it down in the second half against Green Bay last year. It's also how they slowed it down against the Patriots, to the point Brady had to force the ball to Gronk.
You stay in base D, you tell McClain to follow the slot receiver and run through anything in his way. You shade your safety to the outside so he can get a jump. You have to make the receivers and the refs think about it. The last thing you do is just sit back and let it happen over and over like we did Sunday.