thought it was intentional because of the randomness of it all, but actually blizzard makes the client sort of copy+paste the world map into the minimap area and disables rotating.
reckon it's a bit of extra coding thats needed in order for the realui minimap to do the same as there's no pre-defined image in the games database to load from the layers.
no clue if it's just realui or if other minimap addons have the same issue.
It is caused by fact that Torghast use separate minimap frame - a new hybrid minimap. Never used RealUI but I guess that this minimap is rendered behind customized normal minimap - that why you guys see only darkness. Because that is displayed in Torghast on default minimap.