More guild vs guild related events. Not just TW. Give people a chance to have a reason to join a guild and earn stuff (preferably EXP related items like caps, pots or actually exp like 50k or w/e).

Show how strong a guild is or how well they work together. seeing as there is so much guild rivalries no matter what it is you do or how nice you try to play or get along, there is always bound to be a group who hates another group. sadly.