Yeah, roundabouts will mostly be useless if the load between all roads is not balanced. What I do is I separate industrial districts (the heavist traffic generators) into two smaller districts in opposite directions and connect the other two roundabout directions to highway interchanges. That will force traffic to move in all directions.

Although, in reality, you should be connecting each industrial district directly to a highway. Trucks shouldn't even be near your city center :)

So it didn't seem to work much better than a regular roundabout, but I have a feeling that it's more because of the way my city was set up. The majority of the traffic through this roundabout was focused on only two of the four directions, so the traffic got congested on the one-lane ramps, especially so if traffic managed to back up to the edge of the roundabout.

Doesn't make it any less awesome a design though. I will definitely keep using it, even if not as a main juncture!

Awesome! I'll wait for your results.

Gonna stress test this as the center of a larger city (30/40k) to see how it holds up as the joint between residential and industrial sectors. I'll let you know how it works out. :)