Recently we've noticed a severe drop in the mobs that are spawning across our server, I personally frequently see it at 4-5 entites around, when I know that there are dark caves within range that should have spawned monsters. The highest I've seen it since the update was at 20, which was while I was lighting up caves.

Another player reports that he frequently sees entity counts of 1, even while standing at a previously functional mob farm, which has not been modified.

EDIT: This is linked to a change in view distance setting by the server, which means this bug is a duplicate of this

https://mojang.atlassian.net/browse/MC-2536

Apologies minecraft team.