El Mahdi
Muad'Dib of the Anauroch
I doubt it was intentional (at least as a direct intent). One thing I heard from my association with WizKids is that quality often takes a dip annually.
I was told that a lot of employees at the factories in China tend to leave around the Chinese New Year (or take long periods of time off). The factories have to hire and train large percentages of their work force and that tends to lead to regular dips in quality.
I don't think it was intentional in that they're intentionally making them with less quality. I just think somewhere along the way they decided on a cheaper way to make them and the painting suffered as a consequence. At least that seems like the most plausible theory to me (of course this is by no means a statement of what I think is fact, just my theory, I could very well be wrong - my wife could definitely attest to the fact that does occasionally happen

And I do agree with you, pukunui. There have been some good minis in every set. In fact IMO, there have been some really good ones in each set. It's just the ones I've seen so far in the previews haven't had paint jobs that impress me very much (however, there may be some I've missed - I seem to be spending less and less time at the WoTC site).