Actually, based on the enemies he's defeated, those stats seem pretty reasonable. He has lots of trouble with a Balor, as one would expect with those stats. A gimpy elven fighter devises a trick that would have killed him without outside help. Giants still pose some threat to him. He kind of needs weapon finess though.
The different wealth levels for NPCs and PCs explain most of his weaknesses. For special, highly active NPCs, PC wealth might be appropriate but risky if the PCs kill the character and take his stuff.
Also, I think the stats aren't exactly up to date from some of the more recent books. I don't think Entreri is given his artifact class sword for example. The stats also only use FRCS and core books. If you use additional splat books, NPCs should be given appropriate feats and prestige classes from those books, if they're going to be worth the trouble. Drizzt could use Tempest or some of the MotW 2 weapon feats.