Yes, because the average receiver in the NFL is around 5'-11" as well. Not a whole lot of players over 6'-0" have the strength, speed, and coordination to be a very good receiver. Nine out of the top 10 NFL receivers in 2012 were AT LEAST 6'-0" and six of them were over 6'-3". The reason for this is that they are athletic freaks that are as fast as the shorter guys, but have the height and strength to give them a huge advantage. If you'd like a link to that information, I can gladly show you. If Megatron was 5'-11" and 190, do you think he would be as good as he is? Heck no! Deon Butler is one of the fastest receivers in the NFL, as is Jacoby Ford. Neither of them are anywhere close to being elite receivers because they are very short, which eliminates advantages like Megaton, Vincent Jackson, and other tall athletic freaks have.
That being said, good luck again covering our tall receivers. When guys are as athletic as Montgomery and Lazard, they have a HUGE advantage over your midget secondary.