I only tone them down by saying that every UU has a weakness. Some UUs are good at everything, so I just calculate them as 10 times more efficient in everything than a human soldier. But a specialized UU is very powerful but has one or two troubling weaknesses. In example, Khemri's vampires, while very difficult to lay a sword upon, are vulnerable to arrows, expecially if they are burning. These horrors will be difficult to control, and without enough magic to keep them under control they'll break free and go on rampages.