I think they know what to do to increase server population but its not easy or maybe will become some troubles:
- Fix Hellground core walls, textures or whatever is wrong cause its not funny to be facing fe Lady Vashj and have 3 or more elementals going through the stairs and been unhittable till they are on Vashj face (Striders and Nagas included)
- Promote PVP with events, custom BG or arena challenges or any idea to take back those players that came here for a good pvp lvl (or get new ones)
- Promote server popularity taking all youtube videos back.
Maybe some higher rates will improve server pop too but people value more a HIGH lvl end content.