There are a number of posts above that I could respond to on drafting but I'll just make a general one instead. I don't know how well Boston has drafted since Chia has been here, and I don't think any of you do either. What you need to do is compare his number of picks and drafting spots and results to other teams to see whether he is good or bad. My guess is the B's are above average since Chia was hired. He has definitely used the draft very well though. It isn't all just about drafting.
It is also about using picks and prospects to acquire other talent. Providence is winning this year and they have promising prospects left in the system that will join in the next couple years. The Bruins have also won a Cup largely because of the trades Chia has made using picks and other previously drafted talent. Most of the current team are previous draft picks, picks from Chia, or players acquired through some use of prospects & picks. Chia has also mostly correctly identified what previously drafted talent to hang on to. So lets take a look at some of what he has done.
Previous draft picks still with the team - Bergeron & Krejci. Pretty smart to hang on to these 2.
Draft picks on team since Chia - Lucic, Marchand, Seguin & Hamilton (from draft pick Kessel). Also Caron & MacDermid.
Other moves related to previous picks or future draft picks:
No longer here but huge in winning the cup - Got Recchi (+ a 2nd) & Kaberle for Lashoff, Karsums, Colborne & 2 picks
Got Rask for Raycroft.
Paille for a 3rd and conditional 4th
Kelly for a 2nd
McQuaid for a 5th
Horton & Campbell for 2 picks & Wideman
Seidenberg & Bartkowski for Bitz, 2nd & Weller
Khudobin for Penner & Lehtonen
Players identified before doing anything in the NHL (basically free draft picks):
Got Wheeler without having to pick him - later traded with previous pick Stuart for Peverley
Got Svedberg without having to pick him. Huge for Providence this year.
Also traded for another teams pick - Boychuk before he did anything in the NHL
Other promising picks or players acquired from previous picks
Soderberg for Toivonen
Spooner
Koko
Knight
Subban
Camara
etc.
Almost the whole team is from B's picks or derived from them since Chia has been here. Even Ference is a derivative of the Thornton trade.
Only current free agent signings are - Chara, Thornton, Pandolfo, Johnson. Ryder was too.
So even if he hasn't drafted well, which I don't think is true; he has used it to build one of the best teams in the league the last 4+ years with some good young talent left in the system. Keep that in mind when evaluating his drafting and don't forget to actually evaluate it instead of focusing on the missed picks. Most draft picks especially after mid 1st round don't have a significant NHL career.