I find it fascinating that the RP servers, though a tiny fraction of the population of total servers, have some of the higher populations.
I've little to say about your numbers in general but thought I'd comment on the RP server bit. In games that I've played since WoW I've found RP servers generally to be a pretty solid place community-wise with a typically steady and solid population. To broadly and crudely generalize, RPers tend to focus on very different things than the rest of the MMO crowd and appear significantly less fickle when it comes to game/server hopping.
Regarding the numbers, my server's not on that list but I never have any problems finding PvE or PvP activities.