I don't think you understand what the NFL is looking for. They aren't killing their draft stocks at all. They are demonstrating other skill sets that the NFL will value and showing they can be complete every down players. While I personally think we are a little too conservative at times on defenses, especially in teams that should be overmatched by our line, Simmons learning to drop into coverage isn't a bad thing for his NFL future.
I think I also saw you (or maybe it was someone else) complaining that Hill's stats are way down this year. I think people forget we played 16 games last year. He had 113 total tackles (59 solo) or 7 tackles per game (3.6 solo). This year he is averaging... 7.5 tackles per game (3.8 solo). He has lower sack numbers (but those tend to come in bunches), but has already matched his interception total (1) and nearly matched his FF total (4 last year, 3 this year) in 8 fewer games. Simmons is averaging .8 sacks per game vs .56 last year. His total tackles per game is about the same as last year (3).