Server transfert, advice needed!
Full servers are a problem. Your options are 2fold.
1. Wait. One of them will drop to high eventually.
2. Both of you transfer. Pick a server that’s not currently full, and both of you transfer at the same time.
As for guesting, No, it is not currently working. However, you CAN still group with him, and if an overflow instance of the map you want to be in exists, you can get into that overflow and play together. (Join party together, right click on his portrait, “join in <name of map>”)
At the moment… the only maps that really ever have overflow is Lions Arch. So you’d be able to do Fractal runs with him, but that’s it.