Perhaps this is only me that is concerned about this issue, and maybe its not even an issue at all. What I've often thought about is the lack of exp areas in the game. Before this was fine, but now with bracers of speed, they just don't hold up. I can with unique bracers keep half of the exp areas cleared myself, and while this isn't much of a worry for me, anyone else who is on may have a hard time finding a area to exp that isn't being slaughtered all of the time. When someone comes on, and sees another exp'ing like mad and realizing that there isn't much exp to be had they just leave. I think this is part of the problem of having a low number of characters online at a time, there just isn't enough exp to support all of them.
The best solution would be more exp areas, especially designed to focus on certain levels of players. Like easier places for lower levels, and the places with the most exp should be hard to stay in, like Styl and Masadorn. Split up the characters ex'ping into appropriate areas and it will help to keep larger numbers of players online.
I think a temporary solution to this would be to simply increase the rate at which the mobs re-pop, or double their numbers or whatever. But the long run solution should simply be more areas. Bracers of speed really changed this part of the game, now someone with uniques can kill a mob 3x the speed they could before, keeping exp areas empty and lower level players away.
Just a thought, what do you guys think????