Nidoking is surprisingly a very good special attacker because it has access to the ability Sheer Force. Sheer Force increases moves with secondary effects (Thunderbolt, Ice Beam, Earth Power, Sludge Bomb etc) by 30% but removes the secondary effect so moves like Ice Beam now have 117 power as opposed to 90 before the Sheer Force boost. Sheer Force also effects Life Orb removing the secondary effect of HP loss and increasing the already 130% damage output to 169% (1.3*1.3) which is significantly more powerful than a Choice Band/Choice Specs boost just you can change up your moves. What makes Nidoking so brilliant however is its very wide movepool with access to all kinds of moves. It uses its relatively disappointing special attack because it's physical movepool fails in comparison to its special movepool with a lack of powerful moves that would be boosted by Sheer Force.
252+ Atk Rhyperior Earthquake vs. 0 HP / 0 Def Mew: 190-225 (55.7 - 65.9%) -- guaranteed 2HKO after Leftovers recovery
252+ SpA Life Orb Sheer Force Nidoking Earth Power vs. 0 HP / 0 SpD Mew: 204-242 (59.8 - 70.9%) -- guaranteed 2HKO after Leftovers recovery
As you can see, Nidoking with max SAtk and Life Orb has a more powerful Earth Power than a max Atk Rhyperior Earthquake (140 base ATK!) on the same stat spread.
In this instance however, Surf would not be recommended on Nidoking. It will still dish out a fair amount of damage however doesn't get the Sheer Force boost and means losing out on important coverage that would get the boost.