Interesting. Well I've always had my 933L connected and it's been working. I do know that my DNR-202L does some bandwidth hogging so I turn it off when I'm gaming at night. One thing to think about, a camera is recording video or producing video. It's designed to be online ALL the time and thus users who connect to them want to see the video. The video stream is online all the time and when associated with the MDL service, it's just there and waiting for them all the time. I presume there would be some issues and problems if the design was different and harder to trouble shoot problems if something like On-Demand video streaming was in place where the camera would only stream video when accessed by a user. Would be hard to troubleshoot streaming problems in this kind of manor rather then the camera being online all the time. Besides, I presume all cameras maybe like this anyways and been like this for a while.
You might connect up one of the cameras via LAN wire and look at the networking activity on a LED if you have a switch or router that indicates network activity via LED. East way to see visually.
You don't need top tier ISP services for a few cameras. I had 50/3 with my one 933L however maybe higher is needed for more than 3 or more.
I used my ISP default DNS addresses in the DNS boxes on the camera.