I had that problem for the 7 years that I played the game. Often couldn't even get 3 for Dungeons.
I think a major issue with the game became that the most compelling new content, and the content they spent the most money on, was Raids and they were inaccessible to the vast majority of players either due to lacking 6 to run them or the difficulty of the content. And when I say difficult I mean that a lot of what was required were memory tests to memorize symbols and the order things had to be done in rather than difficult combat challenges. Raids became more like math tests than fun combat challenges.
I don't know how you make a game that invests so much in Raids as end game content but only somewhere around 5% of the player base has actually finished a Raid. And I bet the percentage goes to like 1% that have actually finished all the Raids.