when they reworked the mob ai they changed how blazes worked therefore it is assumed this was intended
I would assume that the difficult from .75 to 1.5 would affect spawn rates
are they getting json errors? if so i may be able to confirm the issue
it's a graphics glitch not a generating glitch not sure exactly which java versions/os version/graphic cards it effects but to fix exit the world and reload everything should now be visible i created a new issue track properly describing the problem MC-83499
relogging fixed the glitch not sure what caused it
This is where the new portal took me in survival no structure or island generated on teleport have duplicated on this save will test another save
no can confirm no end dungeon spawned for me at all not plants or anything
EDIT: there apears to be structured and mobs but are not rendering properly images can be provided
A really good demonstration by Eta740 http://imgur.com/a/smMcB It's not that they are updating slower which can be minimized it's that they are updating randomly which cannot be relied upon in a build where you need a precise clock.