To go with my thoughts on there not being a "base defense" anymore, and Carolina looking to stay with some 3-4 packages again this year, I figured I'd post this:
Suggests that base defense is, in fact, slipping in its usage. The article suggests that "base" defense was used 45% of the time, in whatever form, if you assume base means 4 DB. The league used nickel 40% of the time - obviously almost as much - and dime 12%, combining the two for an advantage over base.
Is the average strongside LB really that much greater of a starting force than your 3rd CB anymore? Clearly not.
So let's not get too hung up on scheme, especially in this division.