Well I've been playing since they launched and haven't had queue issues or login issues of any kind. When you login you go through max 2 servers AFAIK before getting the realm list or connecting to your realm you play on. If you time out connecting to your realm you'd be booted back to the realm list. (as if you're trying to login during a maintenance window). It's only when the authentication times out that you're booted back to the main screen.
To check, in real-time, if there's any issues with Blizzard's server (or your realm) you can go to:
http://eu.battle.net/wow/en/status
"Population" is a real-time indication of how many people are currently logged into the server (it doesn't indicate how many people/characters are created it on it) and it will also show you if there's any queuing going on. Since you're booted to the main screen and not getting a message "You are number 149 in the queue, please wait approx xyz minutes" my guess would be that it's the actual connection between you and them.
This is where your ISP can come in. However, I'd try resetting the router to it's default settings and set it up again just in case. Also check your line noise levels (noise margin/attenuation) on the router itself. This will give you more ammo when talking to support and shut their "its not us, its you" excuses since it wastes a **** load of time.
If it doesn't happen all the time and there is no way for you to reproduce the issue, my guess is (and I'll go out on a limb here) is it could be the ISP where it "Connection Reset by Peer" message you (which you'll never see when a connection abruptly ends in WoW like this) because they'll drop the connection for some stupid reason entirely. (This happened to me on iBurst a few years ago when they first started and then ****ed around with their routing/shaping policies)
Another thing I want you to try before contacting WA support as well is to play on the other ISP you have (boo hoo, you'll have a higher ping time maybe... but still
) and see if it does the same thing after a week or two (or how long it takes to happen). This can rule out your end entirely, especially if you switch back to WA and it happens again.
The reason why I'm leaning towards WA having the issue here and not you or your router, is because WA has had several instances in the past year where they will tweak their shaping rules on their end, and entirely **** with WoW. (There was also an instance where WoW, in preperation for Cataclysm, switched to P2P traffic, which was shaped to hell by them during certain hours etc)
So looking at their track record (and the amount of times/days I had to complain and "prove" the problem is on their end) I'm sure that if you work with them you can get the issue fixed in a matter of months (I'd say hours/days, but they're not like that anymore since you have to jump through all the support hoops and spend R600+ on phone calls to support just to sort everything out)
But hopefully Jeff-fa-fa is on the case and can get the wheels turning faster. GL
