I would prefer it requiring it to be surrounded by 8 lava cells.
Industrial Diamond + 160,000 EU (In Lava)+ 8 Tin + 3 Machine Operations = Diamond
A great idea regardless of the amount of lava/items are required, and adding Diamond Dust could result in other people getting new ideas involving it. New machines and what not.
Actually, only 2 tin. 1 craft takes 4 tin and produces 16 cells. It requires 8 cells. Divide 4 by 2, you get 2, not 8.