Not completely exit the client, but return to the "Start Screen" or character selection screen.

SE has done it on previous releases where the congestion was severe, but personally I really feel like it would be best for their server loads, and probably ISP routing if there were less "useless" concurrent connections to their servers.

While you can now World Visit to the least congested shard, I think a lot of people would really like to avoid such "workaround".

I'm frequently having to hop between my main and my alts, and having a queue of 5-50 people everytime, while I see people AFK in the main cities for a day, and some even weeks!