06 Jun 2011 at 04:05 - 2
Tyrian and Northern travel in the south, Canthan in the northwest, and Elonian in the northeast. Once you get them memorized, it's not that hard to get where you want to go.
Grouping them close together may defeat the purpose for what may have been originally intended - groups would form in designated areas based on the campaign whose content they would be interested in doing. Putting all of the travel NPCs together would also push every group together, resulting in a mess of players.