You and some folks here are overlooking a big fact here. Dungeons =/= All Locations.
Remember, there are still landmarks, cities, settlements, buildings, towns, unmarked locations and even shrines. This could make up for 200 locations.
If the OP quoted correctly, it's "Five big cities and more than 130 dungeons."
I just counted all the dungeons on a full-scale Oblivion map. I made it to 213 totally. Perhaps it won't be as bad as I think... but perhaps it will be. I still think 130 would be too much for a size of Oblivion. I'd say rather 70 for a size of Oblivion.
But 70 would be too little then. So the map would have to be bigger...
It's a tough situation, I think.
Pretty sure it's also too late to increase the map size...
So all I can say is -sadface-