It's odd that the three main hotspots are equidistant and matching. The three on the flywheel are where bolts are fitted to the other side. Also there's a lot of play (not rotational) between the centre boss and main mass of the flywheel.
There are some other areas of heating but I would estimate they cover no more than 15% of the surface. My guess is these are all high spots and represent the total clamping area.. Might therefore explain the slipping which should not be that bad, even with a standard clutch cover.