bayou,
Your guess is quite correct, those bumps are where the bolts that hold the paddle to the spar underneath are faired in to make them a little smoother.
I would bet they make the blade a little draggier, but the effect is probably unmeasurable.
The S76 TR is the same as the Black Hawk's but was developed about 3 years later. When the 76 design was being finalized, the BH was going through a bit of development angst where the bonding of the paddle to the blade spar was working loose. There was a recurring ultrasound inspection and the chief S76 designer decided to use a "belt and suspenders" approach, so it is bonded and bolted. Since then the hawk process was squared away, so it dropped the inspection.
Glad you like the 76, I have always found it an "honest" aircraft, no corners where it tries to bite you. BTW all models feel the same, they differ by the top end power. Good Luck!