One thing I can praise in GW2 is the Dynamic level adjustment system. http://wiki.guildwars2.com/wiki/Dynamic_level_adjustment
Now take something similar to this and add it to the Dungeons. No I don’t mean make it so everyone comes into the dungeon as a level 80.
What would be nice is if 2 or 3 people are wanting to group, they can, and the dungeon will level down to meet the size of the party.This way if no one is hardly on you can still do guild runs.
Also have you had a time in your guild, where you ask does anyone want to go do a dungeon and 6 people all want to go with you, making you have to put 2 people out. With a dynamic level adjusting dungeon, you could group 7 people together and the dungeon would level up to meet your challenge.
I guess there should be a max on the most you can have the dungeon level be. So maybe a max party size of 10 should be ok…don’t forget you could group up anywhere from 2 to 10 players. So if you end up with more than the limit, say 12 you could split into 2 groups of 6.
Which brings me to another suggestion; Having 2,3 and 4 guild groups in the same dungeon going though the same instance, but doing different paths that could culminate into one final boss fight with a challenge and reward worth a guilds participation. Maybe this could only be done once per week and have the final boss drop a chest with rewards that will give the “Guild” something. Individual rewards would still come from the regular chests with reward tokens and normal loots. This could possibly be an answer for some of the people who think this game needs raids.
Now for what that Guild reward is , let me know what you think it should be.