I'm planning on trying it at 50 at some point, but, on its face, it seems like a specialized 1v1 gank spec, since it is reliant on multiple DOTs ticking away.
For something like Huttball, which is what I get more than 50% of the time, DOTs are not ideal for a melee train and the assassin tank options provide utility and survivability on a map which is very hostile to melee DPS. So its hard for me to see madness being that great in Huttball. DoTs in Voidstar obviously have their place.
That said, I theorycraft that Madness would be a great 1v1 spec, but all the vids I see of Illum make me wonder whether there is even a place for a 1v1 spec in the game.