I disagree.

The whole point of cooling is because the case is closed. If the motherboard is just sitting out there in the open, why does he need air blowing on it.

The argument that the heatsink was not making good contact with the hexfets... Look at the thread in the Chinese forum. There are more pics. You can clearly see the indentation of the hexfet on the thermal tape. It WAS making excellent contact. I would have gotten rid of the tape alltogether and used paste plus small bolts instead of spring clips, but it still shouldn't burn up in flames like that.

Even cheap MOSFETS just pop and die when they fail. This thing was literally starting to ignite.