Blazes spawned from blaze spawners seem to have no path-finding AI.  Pre 1.11, once a blaze descended to a block, it would spin a bit, then start moving around, usually path-finding on a diagonal.  Now, they just descend to the block, and sit there, only moving when their hitbox collides with another entity (usually another blaze that spawned and descended on top of it).

I haven't been able to evaluate blazes naturally spawned in nether fortress boundaries (explicitly not those spawned by a spawner).

I've searched around the different bugs for different platforms and don't see anything describing this exact issue.  Additionally, the 1.11.0 release notes do not mention this type of change for blazes.  I did notice a 1.11.1 "fix" about spawners not obeying light level rules, which may be related to this, but may not be.