Considering the gap between the final released content and Heavensward's release date, SE is doing quite well compared to most MMOs. WoW was mentioned earlier. WoW's last expac had a 14 month break between the last content release and the expac release.

While not all the content in the game may appeal to all players, its still content. SE has a broad playerbase with different tastes and has to try and cater to all of them as best as they can. When Heavensward releases players will have a lot to digest. The three months between now and that release aren't really that extreme.