Not to be a wet blanket, and not to enter the 'athleticism' argument, but Harris would be rated higher but for the fact that he has distinct limitations in coverage, meaning he doesn't turn-and-run well. Someone in this thread stated that Harris is one of the highest rated LB's for coverage in the draft. That is some kind of mistake since the profile/reports on him I've read said the opposite. He can drift back functionally into a zone but doesn't have the feet to stay with quick receivers ala Dallas Clark.
Harris moves well sideline to sideline and steps forward into running plays with confidence, he sheds blockers and slides through the "trash" well to locate the ball, he hits hard and reads plays/blocking schemes very well. While he'd be a bit more mobile, Harris would be more of Ted Johnson type than anything else, which would be quite fine with me, especially at 28.