I don't think you can blame the recruiting of short DB's on the staff. Look at the NFL. How many 6'4 guys do you see playing DB who run a 4.3 40? How many DB's out there have the stature of a Randy Moss? If they do, they're playing receiver. That being said, I don't think there are many itty bitty's like Grixby playing in the NFL as a DB either.
If you go and look back at some of the great DB's who've played here at NE, I don't think you're going to find very many much over 6' tall. The biggest problem with our secondary this year is that they are so damn young. We've played a lot of freshmen before at DB, but usually when we did so they were playing with a bunch of upper classmen. I think Ralph Brown played a lot as a frosh as did Booker and Craver. It's nothing new to play DB's early, but you just can't play them all early with little upper class leadership on the field. On the bright side, these guys should be a lot better by the end of the season than they are now.