As Hortus' old signature used to say, "Random does not mean fair." Player Dotsofdeath reports over at the World of Warcraft forums that there seems to be a bug with regards to the Transmute sub-skill for the Alchemy profession.

As the player explained, he had been having no luck getting procs over the time he attempted to transmute certain materials (skyfire, earthstorms, etc.), and that other players were reporting similar problems. Blizzard representative Hortus dropped by the WoW Forums to explain that it's not a bug:

We've verified that tradeskills are procing correctly. The nature of random chance and very large numbers means that sometimes somewhere some people will have long streaks without procs, and sometimes somewhere some people will have several procs in a row.

To put it simply: It's just a matter of bad luck. If you happen to be among those having the same problems as Dotsofdeath, cheer up. After all, it may just be a matter of time before you start cashing in on those "procs in a row" that Hortus speaks of. Drop by again in case we run into any more related reports.