Some combo finisher can do it yourself (self combo).
Unfortunately there seems to be NO complete info about combo for all classes yet (but elementalist
have, luckily. Sorry for other classes

) Gonna search harder with uncle.Google....
And about WvWvW queue... Note that there are
FOUR (4) WvW maps. You can imagine one map = process by 1 server.
So, the population of a world (example: SoS) will not simply flood into one WvW map. If you found one WvW map can't enter, try a different one.
Also, we have a new function to enter WvW. We
DON'T need to camp in the mist anymore.
Just press B, and pick which map you want to enter. If you asked to queue, just confirm and continue your other work while waiting for spot.
As for playing with friend, I suppose there is a "JOIN" function somewhere (later) that you can use to jump into the same server with your party. Not sure about this but I read it somewhere.
Overflow server is "extra space for every world". So in overflow server you'll meet with people actually from
different worlds. And of course, you can do whatever you want, all progress saved/tracked. It is just like being in the same main server.