There was a display in the Business Centre in Llandudno Junction a couple of weeks ago showing details of possible new road layouts for the big roundabout at A55 junction 19 ... some had three lanes, some had traffic lights and there was a version which had roads going through the middle of the roundabout. To me, a couple seemed reasonably good.
If they go ahead with traffic lights then getting the sequence will be curcial. Three lanes, with directions painted on them, seemed good as well.
As someone who regularly comes from Llandudno Junction to join the roundabout I am always wary of a car coming round from the south in the left-hand lane and indicating left - looking as if it will turn towards Junction but instead drive across the front of me and goes north on the A470 to Llandudno - the junctions are too close together and the drivers not indicating correctly.
At the end of the day what it needs are drivers who know how to indicate and be in the correct lane. The scenario you describe about cars heading towards Llanrwst happens often - the car in the left hand lane looks to be going to Mochdre yet cuts across the car that is correctly in the right-hand lane heading towards Llanrwst. Drive as if the others around you are idiots, as they often are!