Consider Exiled ones?
Well, I can't say we're the best guild out there as we are just starting out ourselves honestly.
We've got about 5 unique players on emp side and 5 on rep side. (not all the same for both sides)
As a guild we've done many warzones and quite a few flashpoints however we're still in the process of building so we are not all on all the time. We're looking for solid members who want to recruit and want to play. We have forums, a C3 voice channel, a guild stronghold and guild bank.
Whether you decide Exiled one's is a fit for you or not I hope your search for a guild concludes with the right home and you enjoy your adventures in the new expansions. Maybe I'll see you around in game.
Good luck,
Necrid