I dont think you can look at it in a vaccuum. Take Seymour for example. Seymour not being here in 2009 should be compared to the return on the investment. You really cannot look at Seymour of 2010 and beyond because his contract was up. We needed to use the tag on Wilfork and we eventually gave Wilfork a huge contract. Has we not traded Seymour, there was very likely a choice between Seymour and Wilfork in 2010, either with the tag, or with the cap cost. Even though there was no cap in 2010 both contracts would have extend a lot longer, and even if both were still here there would have to be numerous other players not here to make up for it, and there is simply no way to determine the net effect of Seymour or all of those other players.
In hindsight Seymour here in 2009 would have made no appreciable difference to the outcome of that season, IMO (I think that is a well agreed upon opinion) so the trade was good because instead of no gain in 2009, the same thing in 2010 (no Seymour either way) we now have a #1 pick to contribute in the future.
Only if you think Seymour in 2009 was the difference in winning a SB or feel we should have kept him instead of Wilfork, OR think we should have 2 of the highest paid DLs in the NFL and forget everything else, is the trade a bad one.
Saying that the RDE position has gotten worse so it was a bad trade is either the most myopic view possible, or an attempt to purposely slant the argument in the direction you wish to support, facts or not.