I have to agree with Matthew - if it were clearly 5 adds, I wouldn't have asked the question.
In his definition of x dex, Eric Wulff said
"Toe blurriest 6 1,2,3 (x-dex, x-dex, butter-dex)"
I would have to say that if plasma gets an x dex, I think fusion should as well.
I don't really think it's a question of the diffilculty of the move, for me it's a question of how the move feels. It doesn't have the same contortion feel that moves like atomsmasher, reactor, sumo etc. have. There isn't any hard hip twists. The only reason the move is any harder than a legbeater is speed - you need a fast atomic set and a fast double down, apart from that, it's almost entirely like a legbeater.