I know how GW2 can be fixed at a very low cost to ANet, and a staggeringly huge return, allowing them to focus on providing big, meaty expansion packs, unlockable cosmetics, and feature updates.

It's quite simple:

ANet should release a construction kit, similar to the ones that come bundled with the Elder Scrolls game.

Each quarter, there would be a contest. Would-be developers would submit an instance (raid/dungeon/fractal/skirmish), along with a full preview/hype video to ANet, who would review them and put them all on a page for the community to vote on. The winners would receive <insert really cool rewards here, maybe a set of alternate-art Exotics/exclusive title and a cash prize or something>.

The top 3 would be wired together, end to end, on a new map called "The Crucible of Worlds." The loot tables and gathering nodes for each instance in the CoW would be randomly generated each day.

Each instance cleared would reward one Crucible token per day, which would have a dynamic exchange rate for each available type of map/dungeon currency/champ box based on demand.

ANet could also easily implement a player-designed cosmetics tab with another contest, for items that could be purchased with Crucible tokens.

From there, you just build the Crucible of Worlds out, one map at a time, end to end, with a portal like they have in raids at the end of each three-map block.

Each year, you'd hold a grand contest to determine the community's favorite maps from that year's Crucible, and they are either remastered and integrated into the base game as dungeons by Anet, or used as the seed maps for the next year's Crucible. The developers of the champion maps would have the opportunity to meet with ANet (maybe work /at/ ANet?) and help shape the game moving forward.

Bam- infinitely replayable fresh content, churning out fast, with balanced rewards, in a way that doesn't impact the base game but gives the community something to do other than bother ANet about content droughts.