[rekops]

The right thing to do is obviously to be on the defensive,

Correct usage is to be in Rt lane only if you are taking the first Rt turn.
You need to be thinking as you are approaching the roundabout, where you will exit.
If it is any one except the first turn, you need to be in the left lane.

As an example: you are traveling south on Buena Vista and approacing the circle at Belvedere and Winifred. If you are exiting for Belvedere, you need to be in the Rt lane.
If you need to continue on Buena Vista, or exit to Winifred or U-Turn to go back north on Buena Vista, you would need to be in the left lane.

Ok , My wife and I are both civil engineers (wife specifically a traffic Engineer) and understand what is correct, and what actuallty happens.It will never be perfect, but believe me it would be much worst with traffic signals at each 4 way intersection.
If you nchecked accident statistics of accidents from folks running red lights down here, it would be scary.