Yes, there is a bug happening with some of the structures in some worlds spawning inconsistently. If you re-create worlds using the same seed string, you may find that the blaze spawners will generate in some of them; whereas, it just didn't generate in your current version of the seed. I have tested this several times using copies of the tutorial world and tutorial seed string. The blaze spawner in that world has failed to generate in some of the copies I've generated; but has also generated in some of them. Changing the world between various modes and difficulty settings seems to have an impact on whether or not the spawners generate; but the effect is also inconsistent.
4J have been working on fixing it and, I'm sure, there will be a fix in the upcoming bug fix update (TU8) and perhaps some sort of "reset" option if you start working in a world and then only later discover that the spawners didn't generate. The idea of a structures reset button is interesting; but my own preference would be to have the bug fixed so that the structures in worlds generate consistently regardless of what mode the world is created in and what modes the user may flip around between before they've explored all there terrain.
Please take a number and wait for your turn for TU8....
Stay fluffy~
4J have been working on fixing it and, I'm sure, there will be a fix in the upcoming bug fix update (TU8) and perhaps some sort of "reset" option if you start working in a world and then only later discover that the spawners didn't generate. The idea of a structures reset button is interesting; but my own preference would be to have the bug fixed so that the structures in worlds generate consistently regardless of what mode the world is created in and what modes the user may flip around between before they've explored all there terrain.