I like 'em (just be careful about your table formatting
*cleanup girl*)...WRT common foes, I'd say make a table of level ranges, then areas.
COT Mages:
Heroes
5-10: Kings Row, Perez Park, Radio Missions
10-20: Steel Canyon, etc. etc.
etc. etc.
Villains
5-10: Newspaper Missions, infrequently in Port Oakes
10-20: Cap au Diable, etc. etc.
etc. etc.
Then have the linked city zones have a breakdown of where to find their main enemy groups. That could be another project to link with this one, to make sure all zones have the most common locations for their enemy groups.