Omni have at least 2 main grouping areas-- Omni Trade and Omni Entertainment. This is where you have both whompas AND grid entrances.
Clanners are all stuck in Tir.
The reason is really simple-- the location of grid and the whompas. Both work together now, especially since the whompas have been expanded so much.
Athen should be a busy town, but because the grid entrance the whompas are several minutes apart, it's largely empty.
The issue isn't so much the Time it takes to go from the Athen whompas to the West Athen grid, it's the social aspect of teaming that matters. You want the grid/whompas, stores, bank, mission terms, all reasonably close.