TL;DR: I loved guilds missions and want Arenanet to either expand or rebuild the Guild Mission system.
I don't like PvE much. I do the story, but I'm here for WvW. When guild missions were new we used to run them on a weekly basis, but after a time we grew bored with them and stopped doing them. If Arenanet had expanded the system with regular new guild missions, I think our guild might still be playing together.
Players play together when they aren't bored with the content - the lack of variety in guild missions could be seen as a big part of why a lot of our guild stopped playing the game entirely. That's a few potential gem store customers instead paying Blizzard or whomever. I think the Guild Mission system is superb, but it NEEDS CONTENT!
Thief OP? Better nerf Scourge ... again.