From reading the Minecraft wiki, it states that a blaze will track a player within 48 blocks, and will attack them from within a 16 block radius with their fireball trio attack. For me in Minecraft 1.11.2, the blaze are launching their fireballs from up to 48 blocks away, which makes them way more difficult than they used to be. I didn't see this as an update anywhere. The blaze are also randomly despawning while they are attacking me.