They've been planning this change for quite a few months now, all in preparation to SLOW DOWN how much dilithium players can make so that they can't level their bases too fast.
"My frozen dairy-based confectionery attracts all the males of the species to the facilities. They all agree on it's superiority. Indeed, it is superior to yours. I could teach you the finer details but that would require monetary recompense on your part." -The Milkshake Song: Vulcan Edition
If anything the price will be going up not down, you now need more.
I was once DKnight1000, apparently I had taken my own name so now I'm DKnight0001. If I ask you a question it is not an insult but a genuine attempt to understand why. When I insult you I won't be discreet about it, I will be precise and to the point stupid.
I also had noticed this and I also Do Not Approve.
There shouldn't really be an issue about starbases developing too fast because of there being lots of dilithium around - you just make it cost more dilithium.
This does shift the weight of dili harvesting more towards daily missions and away from doff assignments; ultimately this is a gameplay issue instead of an economic one. It doesn't impress me that much though since most of the daily dilithium missions get boring if you do them more than a couple times. Meanwhile, now people have Fleet Missions to grind for fleet marks in addition to grinding STFs for borg hardware and Daily missions for Dilithium.
On the plus side though, Dilithium will become more valuable - not only is it harder to get but it is also in greater demand thanks to being needed for fleet missions. This means that sooner or later the Dilithium Exchange will swing the other way, with the price of Zen dropping substantially. It hasn't last I checked though; when you count the change from c-points to Zen Dilithium is actually less valuable than it was a couple days ago, since you have to multiply by 1.25 in order to compare a price in Zen to a price in c-points.
I think in the long run this will be good for the game as it gives the free-to-play people a better chance to contribute to the paid economy of the game and that makes for greater profits for PWE as well as greater participation by players.
I think this would have happened anyway without debuffing the doff assignment though since ultimately the hard limit of 8000 dili per day is still in force.