When I made the decision to start looking for a guild to join i had only 2 criteria: 1) It must be a guild with a large community, and 2) It would be good if part of that community will be playing both GW2 and D3.
In a traditional MMO you dont neccessarily have to have voice chat. Yes it can make things easier but essentially you are force to chat with players in-game whether that is via text or voice because grouping up to do quest is in most cases a requirement. However, in both GW2 and D3 the game design does not neccessarily require you to do a lot of content that requires you to spam in chat LFG (especially with dynamic events). Because of this there is a lot less chat requirements in-game so for me being part of guild that has large community is more about havings like-minded ppl to talk to while i play to keep things fresh rather than a requirement for gameplay.