That is all about durability and defense. Fedor ruled the weight class because he could survive. Whether it was his magnificent timing and reflexes vs. Cro Cop or staying conscious (and alive!) after the Randleplex, the guy could avoid taking damage and keep fighting even after taking massive damage.
If a guy as durable as Fedor or Roy Nelson comes along who is as skilled as Fedor or Overeem, then sure, we could have another dominant champ. I don't think that person is out there right now, though.