Its definitely lower for me, than it was a few weeks ago (around 3.0.3 release, give or take a couple days). But I have only kept actual stats over the last week.
198 total millings for 52 Icy Pigments (0.26 yield). I'd say at 50 stacks of herbs, this is starting to be statistically significant.
Yes, I have gotten 3 icy pigments form a single milling, and had a day where 30 millings yielded 13 pigmets (0.43 yield) - but this day was countered by two other days where I went 38:9 and 31:6
I have not collected enough stats "by herb type" to be statistically significant "by herb type", yet, but am working on that.
I'll continue to keep stats by day, so they can be reconciled by server restarts and/or patches and share when I find anything useful, or different.