Well, to my memory, this as well as pretty close to all D&D decks are made by USPC - I actually can't think of any examples that weren't off the top of my head.
USPC had most of the kinks worked out at the new plant by the time this deck was made, but it's possible for an occasional clunker to get through QC in terms of the glide characteristics. "Finish" is a reference to the card's TEXTURE, not its COATING, so to say that the cards don't have much finish is to call them nearly smooth. Are they nearly smooth?
Another factor that can adversely affect cards is how they've been stored. If the deck isn't kept within a decent range of humidity and temperature, it can adversely affect how it handles - clumping like what you're showing is indeed possible.
I can't recommend or disavow this, but I have heard of people trying to improve their deck's handling by putting them in a freezer for a short while. If you attempt this, I'd put them in an airtight bag first, so they're not making direct contact with any of the freezer's interior surfaces, and I wouldn't put them in for terribly long - maybe an hour, tops. (If anyone out there has more experience than my "none" at this method of deck performance restoration, please chime in!)