Since recently I am facing the same issue, disconnecting every 30m or so.
I also tried the suggested fixes like:
0. rebooting router/PC/game
1. changing security setting in Windows Firewall
2. adding -clientport 80 or 443 option to the executable
3. checking whether the packages don't get lost from my ISP's side via /ip and tracert commands
Nothing helps. I hope this is somehow fixed by a gw2 update or disappears from itself. Although I'm not very confident seeing that this clearly isn't a new issue, but it does look that more people are facing this recently..
Edit one day later: Pretty sure it's just a connection issue from my side after all.. Possbily related to the Powerline installed at my place.