I usually only wear one wicking under layer. A dry suit with nothing under it will kill you when you fall into the water (due to its enormous thermal conductivity). In that case its much safer to wear a wetsuit.

When it gets down to around 10-15 degrees celcius (50-60F) I usually pop on a moderately tight fleece sweater (too loose and the inevitable folds get in the way).

Dennis
PS: there's lots of dry-suit weather here in the Netherlands...