I ran some searches at pro-football-reference.com, for the 4th through 7th round of each draft since (and including) 2000. I've posted links to them below, with one link per season for easier viewing. It's really easy to scan the results, since players in bold are still active, and you can sort by pro bowl appearances and years spent as a starter. You can also sort by stats to get a sense of some significant, non-starting players.
Anyway, in doing this, I learned that our drafts haven't been as bad as I thought compared to what else was available. The truth is this: there's a lot of dreck in the draft after round 3. These picks are, statistically, almost worthless. We're talking a handful -- like 3 to 5 -- guys per round who have any kind of impactful careers. In addition to that, the rate of success plummets progressively -- round 4 is a lot more likely to find productive contributors than is round 6, for example.
In other words, we should restrict our hand-wringing about our draft to any picks we make in rounds 1 through 4, but especially rounds 1 and 2, as those are the money rounds. The bottom line is that Colbert is not missing out on any great talents in these rounds -- because there isn't much there. Drafting an Ike Taylor or a Clark Haggans, it appears, is actually a pretty darn good accomplishment.
Some other notes: maybe this won't surprise anyone, but some drafts are way better than others. Check out 2001 - a terrible draft for these rounds. Then look at just the 4th round of 2006 -- lots of good players in that one round, which is unususal for this sample.
For drafts 2000 through 2003, I spent time picking out players who made the pro bowl (usually a very short list), and those who have started several seasons.
2000:
http://www.pro-football-reference.com/draft/draft_query.cgi?pos=ALL&round_1=4&round_2=7&tm=all&year_1=2000&year_2=2000&conference=any&type=Best players, in order of pro bowl appearances: Beardy (6th), P Shane Lechler (6th), LB Adalius Thomas (6th), QB Marc Bulger (6th), PR Dante Hall (5th), DE KGB (5th)
Other notable players with 5 or more years as a starter or productive part-timer: T Mark Tauscher (7th), FB Terrelle Smith (4th), LB Na'il Digs (4th), LB Clark Haggans (5th), LB Danny Clark (7th) RB Sammy Morris (5th), LB Dhani Jones (6th), , DE Robaire Smith (6th)
2001:
http://www.pro-football-reference.com/draft/draft_query.cgi?year_1=2001&year_2=2001&tm=all&pos=ALL&round_1=4&round_2=7&slot_1=1&slot_2=500&conference=any&show=all&lg=ANY&type=Pro Bowlers, in order of appearances: WR Houshmanzadeh (7th), WR Alex Bannister [?] (5th), RB Rudi Johnson (5th) -- with one each.
Others with notable starting experience: T Rian Diem (4th), G Ben Hamilton (4th), DB Renaldo Hill (7th), DB Marlon Mcree (7th), G Roberto Garza (4th), TE Brandon Manemanelauna (4th), DB Anthony Henry (4th), WR McCariens (4th), LB Ed Hartwell (4th), WR Cedrick Wilson (6th)
2002:
http://www.pro-football-reference.com/draft/draft_query.cgi?year_1=2002&year_2=2002&tm=all&pos=ALL&round_1=4&round_2=7&slot_1=1&slot_2=500&conference=any&show=all&lg=ANY&type=Pro Bowlers: DE Aaron Kampmon (5th), the only guy to make a single pro bowl out of this group.
Other notables: LB Scott Fujita (5th), LB Andra Davis (5th), TE Randy McMichael (4th), LB David Thornton (4th), DE Alex Brown (4th), C Justin Hartwig (6th), LB Larry Foote (4th), DE Brett Keisel (7th), QB David Garrard (4th), DE Jarvis Green (4th), RB Chester Taylor (6th)
2003:
http://www.pro-football-reference.com/draft/draft_query.cgi?year_1=2003&year_2=2003&tm=all&pos=ALL&round_1=4&round_2=7&slot_1=1&slot_2=500&conference=any&show=all&lg=ANY&type=Pro Bowlers: CB Asante Samuel (4th), DE Robert Mathis (5th), a few other one-timers
Other notables: G David Diehl (5th), C Dan Koppen (5th), DB/KR Terrence McGee (4th), CB Ike Taylor (4th), LB Bradie James (4th), LB Cato June (6th), DE Jarrett Johnson (4th)
2004:
http://www.pro-football-reference.com/draft/draft_query.cgi?year_1=2004&year_2=2004&tm=all&pos=ALL&round_1=4&round_2=7&slot_1=1&slot_2=500&conference=any&show=all&lg=ANY&type=2005:
http://www.pro-football-reference.com/draft/draft_query.cgi?year_1=2005&year_2=2005&tm=all&pos=ALL&round_1=4&round_2=7&slot_1=1&slot_2=500&conference=any&show=all&lg=ANY&type=2006:
http://www.pro-football-reference.com/draft/draft_query.cgi?year_1=2006&year_2=2006&tm=all&pos=ALL&round_1=4&round_2=7&slot_1=1&slot_2=500&conference=any&show=all&lg=ANY&type=2007:
http://www.pro-football-reference.com/draft/draft_query.cgi?year_1=2007&year_2=2007&tm=all&pos=ALL&round_1=4&round_2=7&slot_1=1&slot_2=500&conference=any&show=all&lg=ANY&type=2008:
http://www.pro-football-reference.com/draft/draft_query.cgi?year_1=2008&year_2=2008&tm=all&pos=ALL&round_1=4&round_2=7&slot_1=1&slot_2=500&conference=any&show=all&lg=ANY&type=2009:
http://www.pro-football-reference.com/draft/draft_query.cgi?year_1=2009&year_2=2009&tm=all&pos=ALL&round_1=4&round_2=7&slot_1=1&slot_2=500&conference=any&show=all&lg=ANY&type=