When you repeatedly teleport a mob to a certain block, just like with players, it should stay facing in the same direction as it was when it was first teleported. This doesn't actually work, without using the facing command, they still look around when they should do the same thing as a player being teleported. Even if you use the "facing" subcommand and make it face a certain direction. They do look in that direction while idle, but sometimes they still look at you and completely ignore the "facing" subcommand.

Steps to reproduce:

• Place a repeating command block, then enter this command into it:

 /tp @e[type=villager,c=1] ~ ~1 ~ facing ~ ~1 ~  

• Summon a villager, then activate the command block.
• notice how the villager will face in the correct direction if you aren't close to it, but then it will try to look at you when you get close to it, but the head stays in the correct direction.  This works for all mobs.