Your count has to be off, NAS - Marchand played 20 games last year. Bitz played 37 games in A in 08-09 and 35 in the NHL. Sobotka played more games in Providence than in Boston two years ago (25 NHL games). Whitfield's games probably shouldn't count given that you're talking about prospects. You're right about the stinky prospects in Providence but that's a result of drafting that is a mix of great and awful. Great when the players go straight to the NHL, awful when they can't even crack the powerhouse Lightning and Wild rosters, though even then, they brought back value.
Assume that the prospects available from Providence over the last two years would have come from the 2003 draft and later. I go back that far to include potential college or European players who might go as many as 4 years before appearing in Providence. Also assume that you really only judge the viability of 1st and 2nd rounders, though you should probably credit long shot hits in later rounds.
'03 Stuart (1st) and Bergeron (2nd) were regulars. Bergeron made the team as a foetus. Masi Marjamaki (2nd) ... well, he had 118 pim in Finland last year!
'04 No first rounder. Krejci and Karsums in the 2nd. Krejci was a regular the last two years, Karsums got his 14 games before he was dealt.
'05 Lashoff (1st) and Kalus (2nd). Bad drafting. They drafted for position (anyone heard the phrase "puck-moving defenseman" anywhere?). Many great D options they missed, though - Niskanen, Letang, Yandle, Vlasic. Kalus went to StL is now waiting tables at a BB joint.
'06 Kessel (1st) went straight to the NHL, Alexandrov (2nd) wasn't available until now, and Lucic (2nd) made the team in his first camp. Good drafting, no time in Providence as yet for any of the three.
'07 Hamill (1st) Cross (2nd). Cross is still in college, and probably needs to be. Hamill.... But as has been repeatedly noted, this was a lousy draft.
'08 and '09 players weren't in Providence. Sauve and Caron remained in Juniors where, by agreement, they had to play if they weren't on an NHL roster. Colborne was in college.
All told, between '03 and '07, that's ten players picked over four years. Five picks are or were core players, two more were misses who were still strong enough assets to deal for Recchi and a 2nd round pick, and another who was attractive enough to be packaged for a veteran goaltender. That's eight of ten who had some value to the team, and one of the two hold-overs is Alexandrov. Three players went straight to the NHL without playing in Providence. This doesn't inclue later round players like Bitz, Hunwick, Sobotka, Marchand, Ben Walter, and some Versteeg guy who were drafted in the 4th round or later and who have had at least 20 game in the NHL.
That means the players available to Providence are slow rollers and late picks. The P-Bruins have rolled out a lineup of 4th through 7th rounders like Goulet and Bodnarchuk, Nelson and Knackstedt. The rare third rounders like Marchand and Lehtonen end up leading the team in scoring. Hamill is the only skater who came in with a pedigree (Rask being the other player).
Now, before 2003, the drafting was at it's nadir. 2000 was the worst: 4 picks in the first two rounds - Jonsson, Samuelsson, Hilbert, Huml. Hilbert managed 300+ games, but the other three totalled 71 games, 6 goals, 21 points. Also atrocious? The second rounders. Hilbert, Ben Clymer, and Jonathan Girard are the only second round picks in the decade between 199 and 2002 to play more than 100 games. None will be mistaken for stars. Jozef Stumpel was the slump buster. Between 1986 and 2002, the Bruins had six 2nd rounders who never played a game. That would be about 40%, but it's worse if you consider that they also dealt away their 2nd rounder 5 other years. That's well over half. All-pre-2003, their second round record is consistently, bizarrely awful. The best second round they may have had was Byers and Curran after Kluzak - hey, 2500 pims is a victory here. The best player? Mark Howe. Never played a game in Boston. And here's the real kicker: Before 2002, the Bruins drafted only FOUR players in the second round who qualified for an NHLPA pension (400 games): Clymer, Stumpel, Howe, and Rick Smith. Since 2003, they've drafted Bergeron, Krejci and Lucic in the second. I'll be surprised if any of them play fewer that 400 games - Bergeron's almost there, so even his concussion history doesn't deter me. So - the entire history of the draft prior to 2003: 4 players. Since 2003: 3 players.
Bad drafting is relative.