I have noticed that certain things, such as the spikes from Quill mobs and mortar fire are not influenced by Slow Time's 90% projectile slow. What other sorts of ranged attacks fall into this category?
Azmodan's big ball of death fire thing is not slowed...and rather painful.
Idk about the mortar abilites, but I've had slow time effect the straight fireball ability, the posion bees, wind-up melee attacks, and arrow-type abilities (skeleton archers, etc).
My team had a mob that had this ability and our Witch Doctors bears weren't slowed. I have no idea what the skill is called.