MC-49640 isn't technically a bug as it is marked as "Works as Intended" but I think it would make for a very neat AI tweak. Ghasts were actually pretty threatening and dangerous in older versions because they could target and see you from any height/distance, making them more difficult to evade and giving you a reason to actually attempt to kill them ASAP. Nowadays, in my experience, they're barely even an issue and with the nether being pretty bland in 1.12 I think this could spice things up a bit!