I'll counter with the the thought that I really, really, don't want a mechanic that precise for whom might be alerted at what distance by what use of magic. The idea that the use of magic might attract the wrong sort of attention is an awesome narrative tool, and I don't want it sullied with numbers, if you get my meaning. I'd much rather use it as, to use some loose PtbA terminology, a harbinger of future trouble move, or even a harder immediate trouble happens kind of move. In both cases I'd want to use it either flat out in the case of immoderate use, or even better, in a case of failed but moderate use, probably with some sort of countdown clock.
What I don't want, or need, is a blast template. That's too cut and dried for me. Maybe a closer, lesser evil notices, or maybe the necromancer in the far heart of his dark empire does, who knows what might happen. I don't want to constrain a tool as cool as this with anything as plebian as a range. A rough guide might be in order, maybe, but the first time someone tries to calculate how many miles they are from Minas Morgul before they crack off a magic missile I've done something wrong IMO.