The Laanx server is showing in the server list with a percentage number that bounces around (which I assume is some sort of ping).
the percentage number isn't a ping, it's a percentage of packets that made it through and shows it the rate of dropped packets is high instead of the ping
You don't have to open port 7777 on your own PC. The PlaneShift client will use a random UDP port on your side, but send and listen to packets from port 7777 of the game server. So there should be no need to configure your firewall, as long as it will listen on the same port which was opened for sending (which is usually the default).
the "no need to configure your firewall" isn't necessarily true.
it should be configured to allow a udp connection to the planeshift server on port 7777 that should be tracked statefully at least (note that not all firewalls support stateful tracking, but if you're using iptables or something similiar it shouldn't be an issue).
anyway, as some packets get through, your firewall doesn't seem to be an issue (in that case it should be all or none blocked), but some other kind of issue with the network connection.
as a simple test you could start by just pinging the server and see whether you get packet loss there as well.
another issue could be your local wireless setup (check connection is actually stable and working fine there).
finally there could also be numerous other issues that may be causing packet drops (e.g. bandwidth limits and according dropping strategies), but I don't have a generic "check this" for such things :x