Battlemaster functions much the same way, despite it being a unique game in many aspects. Look at game worlds today versus five or more years ago. It's most obvious on the Colonies, but is present on all other maps except Dwilight and Beluaterra. Some realms have grown increasingly large, massive even, and the overall number of realms has fallen.
OK, I see what you mean with that. I thought it was something like that, but I wanted to make sure.
IMO, the reduced number of realms is due to the low player density. Crank up the density, and you'll start to see realms fall apart due to internal pressures. The way it is now, players generally have all the titles they want or can handle. If not, then they would generate more conflict trying to get them. This lack of internal pressure is why you end up with monstrous behemoths like Sirion, Perdan, Arcaea, Morek, Astrum, etc....
There are several game mechanics to limit this kind of spread. As they grow larger there are multiplying penalties that begin to grow, especially if a realm grows out of proportion to the rest of the realms on the island. Perhaps those penalties need to be increased.