I'm really not a fan of cross-server. Having played WoW prior to the LFG system and now, I can say that whilst the LFG system is fantastic in terms of convenience, it's totally delivered the finishing blow to any community that game once had.

I think alternatives such as maintaining versatility of job roles and ease of class switching (but still being able to work towards the same goal through faction reputation rewards etc as well as pure class xp) can help alleviate the need to gather people from different servers, as job roles are easier to fill. (The smaller party size helps too)