You've always got a better chance to win if you can stop someone as means your offense has to do less. It's why the old adage is that defense wins championships exists. Never truer than the year the Baltimore Ravens won with Dilfer at QB. I think the same as true today, only difference is most games now are usually won or lost by two or three plays in a given game.
The reason for more athletic LBs is because the TE position has evolved too, as now it seems like every good team has a TE that can find a seam in the middle of a defense and move the chains. I mean look at our game we were struggling when we let Smythe beat us early on but once we covered him we did better on D. Toss in on the other side Kincaid was a threat against the Dolphins.