Some mobs, like Putridus the Ancient, seems to get loaded into memory even though they're out of the suggested "load" area and thus out of the radars display scope.
I even got notice of him when I was in Dalaran, and he's way out in Icecrown. That was 3 times the radars display scope...
An option to increase the radars visual scope even more in those cases would be nice.
An indicator of the location sounds like a good idea aswell but it might be superfluous in many cases, like when you track lots of objects.