Tends to get overlooked, but this is the worst thing about this launch imo. Having friends buy the game and not being able to roll on the same server as me is something I have never experienced in an MMO before.
When it launched, FFXI by design did not even allow you to choose your server, unless you had a pass from someone already on that server. I've also seen character restrictions in a few other MMOs at launch.
Of course, that's not to say that any of those excuses SE in this case. I would think that a lot of this could have been avoided with better planning and mitigation plans.