Late merges are optimal, and the fact that so many people disagree with this practice (or take it as a personal affront) is one of several gross failures of US driver education programs.

However, yes, complicated roundabouts that require perfect knowledge of what lane you need in order to take an exit you can't see in advance do suck. If you find yourself installing a roundabout with more than one lane, you probably should be installing a traffic light instead.