One survey question regarding seven-hero parties sparked a lot of discussion in the community, and ArenaNet heard the answer loud and clear: An upcoming content update will bring the ability to fill your party with all heroes.
For those of you who love grouping, the other half of this update is for you: "We're going to be adding Embark Beach-a new Zaishen outpost that will allow players to travel to all Mission outposts (that they are eligible for!) from a single location. So if you're looking to find something to do or someone to help you out, you just have to check one convenient location. Embark Beach will be included in an upcoming feature build containing some improvements for the game."
Check out all of the survey results at the ArenaNet blog!