If you have any proof it actually stresses the server, feel free to report them to Funcom using the procedure established in the official rules.
If they built so much, I’m pretty sure it can’t be said they don’t play the game.
The dungeons are optional. You can’t – and shouldn’t be able to – force other players to play your way. As for not being able to handle a Purge, well, that would be their problem, wouldn’t it? If they really build as much as you make it sound, they should be getting Purged fairly often. And if they don’t know how to handle it, then the Purge will damage their builds. At any rate, I have no idea why it’s anyone’s concern but their own.
Now we get to the real point. Blocking roads and nodes is not only selfish and impolite, it’s also pretty much something you can report them for.
I wish people would stop conflating big builds with people who build without regard for others. It’s possible to build big on an official server without inconveniencing anyone.
That’s literally not how it works. They published the official rules a long time ago and the link to those rules would pop up in your game every time you logged in – for a long time – and still nobody seems to have actually read the rules. The way it works is not that Funcom monitors the servers and acts upon what they see. The way it works is that players report rule-breakers and then Funcom can act on that.