Would you mind providing more details with this balancing issue?
What mod configuration (angel's only, +bob's mods, overhaul) are you playing with?
Where do you get excess nickel from? Can you reduce the amount of excess nickel by choosing alternative recipes for the products that have nickel as by-product?
At what technology level do you first experience this issue? Are there alternative technologies that might help later on?
Is the connection to cobalt the recipes for Molten iron (4) and Molten steel (4)?