I've heard others express similar feelings about the extra Basic Cards, but let's break this expansion down by the numbers.
30 Black Market Cards to the original 60, a 50% increase
32 Normal Obstacles to the original 40, an 80% increase
16 Hard Obstacles to the original 40, a 40% increase
25 New Upgrades to the original 48, a 52% increase
0 Crossfire Cards to the original 50, a 0% increase
More than doubles the "available" Missions, from 3 to 8
Not including the extra Basic Cards, High Caliber Ops still adds more than half of the original game and costs less than half the price. I don't see how they could have added more content in this expansion without risking designing themselves into a corner. This way they can see how High Caliber Ops integrates into the base game and give themselves room for future development.
As for the extra Basic Cards, I think you are right that they were filling blanks, but in a good way. 56 is a pretty standard printing batch size for cards (Poker deck is 52 + 2 Jokers + 2 Rule Cards), and printing companies normally charge significantly less to print in increments of 56. There are 112 (or 56 x2) cards in this expansion. 80 of those cards could be considered the "meat" of this expansion. So Catalyst had a choice: Either cut 24 "meat" cards (and probably drop the MSRP from $25 to $20), or add 32 New Basic Cards. I think they made the right choice.