Pretty much everyone uses a physically defensive Clef, so I'll just assume you're using that already
EDIT, you just said you are so yea. Slowbro would definitely work, it's great in this meta. I have a very physically defensive Nidoqueen. Never ran the calc, but she should be able to tank an unboosted Icicle Spear from Cloyster as well as +1 EQ from DNite. She can then deal great damage with either Ice Beam(for DNite,) or either Sludge Wave or T-Bolt for Cloyster. Counter also deals with them.
Electrode outspeeds DNite at +1(pretty sure,) and obviously unboosted Cloyster. SE STAB takes out Cloyster even with a measly base 80 SpA, and HP Ice or Foul Play may do the trick against DNite if it's weakened. T-Wave ruins it at the cost of your Electrode. Arcanine can kinda deal with both provided they're not highly boosted and WoW hits. Blastoise should also be fine against them, but it ain't that good.
You want it either way, but especially for you it's important to have Stealth Rock.
On a separate note,
6tennis, I'm calling you out for saying Nidoqueen is worse than Nidoking. Her greater bulk means she's way better for setting rocks, while being slower doesn't matter so much cause King is sorta slow too, and at least. queen can afford to be slow. Lower offenses suck, but she's still quite strong, and Nidoking's niche in Sucker Punch is largely irrelevant cause that's kinda expected on it and thus easy to play around(I.e. Sub Zam and WoW Gengar.)