TL;DR = Dalborra and Gav Daragon are fine. Master Dar'Nala is lower population and should be merged with some other PvP server.
This is how the pop of the three APAC servers compares to the average server of their types, and versus SWTOR overall. These numbers represent the portion of players left compared to 6/27/2012. So for instance SWTOR overall has about 20% less logins than a couple months ago. Master Dar'Nala is only about 58% of what it was a couple of months ago - it's lost about 42% of it's population. (Link to how I got these numbers HERE
% of 6/27 population
All SWTOR servers 80%
All PvE 80%
All RP PvE 99%
Gav Daragon 92%
All PvP 65%
Master Dar'Nala 58%
Dalborra is actually doing a tiny bit *better* than other PvE servers. Gav Daragon is doing a bit worse than other RP-PvE servers, because it's "only" at 92% of it's post transfer load, but that' means it's doing great!
Master Dar'Nala has lost a lot of people... more than even other PvP servers.