I remember an admin once posted that, if they're red to the max level in the game (which was.. 60?, at the time of this post), that the level was based on difficulty. Such as, if the MOB is red to 70, but easy, they'll give it a 73. A little harder, 75. A good bit harder, 80. Harder still, 85.
Some may be data-mined, but, if they were, I believe there wouldn't be so many errors in them. Whenever the level cap goes up, a number of MOBs seem to need level changes, since their cons can now more accurately place them.