Glowstone Spawn Rates in Nether are lower than in past Versions

I wish I had some hard and fast data on this issue, and this report is somewhat anecdotal, but it appears that Glowstone spawn rates are way down in worlds created in the most recent snapshots. I searched the bug tracker and couldn't find anything, and it may just be the world seed, but it feels like spawn rates for glowstone clusters in the Nether appear to be down by at least 50%