Agree that Brown should be in, I can't believe he still isn't in. But Buffalo wasn't exactly a passing attack back in the day, they ran a no huddle (K Gun) which is what they were known for. They did have that guy Thurman Thomas who was always near/at the top of the rushing leaders, and he was obviously a key point in their offense. I'm just saying you can't discount any of Reed's stats based on him playing in a pass happy offense when he didn't play in a pass happy offense (Kelly only twice threw for over 3,500 yards, and one of those was in his rookie season where he threw for 3,593 yds).
Brown's #s are better than Reed's, and he should be in there before Reed, I agree with you completely. If you look at the stats though, Oakland's offenses were more pass heavy than Buffalo's back then, at the very least they were the same. I wouldn't be using that as an argument as to why Brown isn't in, I'm just pointing out that the opposite of what you said about Buffalo and Reed is actually true.