I think Nidoqueen might actually like Encourage even more than Nidoking. Not to say that she's a better user of it, necessarily, but I look at it this way: If I see a Nidoking in a team lineup before battle (assuming that's implemented), I at least know he's probably there to run things over and can prepare for that. If I see a Nidoqueen, I won't know if she's there to stand around putting down Toxic Spikes like in fourth-gen, if she's playing up her (effectively) base ~110 Special Attack, or some combination of both. Base 76 Speed is also an interesting tier since with the right EVs she could beat Breloom, Metagross, and Tyranitar. And Smeargle, I suppose, but the other three are bigger deals.
Nidoking's attack advantages are clear, so I don't want to restate the obvious, but I will say that it's not like he doesn't also have the ability to use Toxic Spikes if he really wants to. One advantage there is that unlike with Tentacruel, Roserade, Nidoqueen, and Forretress, a person with a Rapid Spinner won't immediately realize the importance of not letting it get KOed just from seeing Nidoking in the lineup.
Also worth a mention if Ninetales is released: the Nidos have 236 power Fire Blast in Sunny Day, which is almost as strong just from neutral damage as their 247 power super-effective Ice Beams and Thunderbolts.