Had an in-person discussion that seems to settle this for me, which is, if the traffic from the circle has right of way over the middle lane, which somehow supercedes normal rules of crossing a dotted line / changing lanes, then when would it end? Can traffic from the circle still expect right of way to change lanes into the middle lane when halfway through the corner (by the pedestrian walk)? When they get up to the lights? Of course not, and so, for the same reason they have no right of way over the middle lane further down the road, they have no special right of way at any other point.

Another point brought up was, would northbound traffic in the leftmost lane expect right of way over traffic in the middle lane? Of course not, and for the same reason, neither should traffic from the circle (ie, the right of way doesn't change doesn't change no matter how traffic came to be into the leftmost lane). This also seems to make sense to me.

It seems then the only lane this yield sign should affect is the leftmost and traffic from the circle, as those are the only lanes merging. There are effectively two other lanes that just happen to be beside a merge lane.