I have a general hostile mob farm near my base (with in the simulation distance).  I farm was working fine at first but when I started collecting mob by naming them using the name tag, the spawn rate of the farm started to decrease until it is no mob spawn at all.  If I kill off the named mob, the farm works again and mobs spawn normally. 

The wiki states that when mobs are named tagged they are no longer counted towards the mob cap but it seems like this new update doesn't remove them from the cap.