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Well, Sauron didn't have a lieutenant that served him as he served Morgoth. Arguably there were the Nazgul, but after the One Ring was destroyed, they were gone along with Sauron.
Durin's Bane had been hiding since the end of the first age, nigh 8,000 years, IIRC.
Most of the Balrogs were destroyed in the war of wrath, and are more intent on hiding then ruling Middle Earth. If they had any ambitions like Sauron did, they would have been more present in the second and third ages. As far as I can tell, the Balrogs were used more like Elite troops then battlefield commanders.
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