Not sure I like Rock either. It's adding on several weaknesses (water, grass, fighting), just to hit Fire and Ice for super-effective (and Bug, but the OU bug types, Scizor and Forretress are hit neutral by both Electric and Rock, due to their other type, so bug isn't relevant, along with Flying, since that's covered by Electric already) basically. However, the only Fire and Ice types really found commonly in Standard are Heatran, Pyroak, Mamoswine, Syclant and Weavile. However, due to their secondary typings, Heatran and Mamoswine are both neutral to rock.
That leaves Weavile, Syclant and Pyroak. Weavile is on the frail side, so it doesn't really need STAB rock to be taken care of; even something like Volt Tackle or Thunderbolt should leave a good dent in it, ignoring other options we could give it, such as Close Combat (plus, there's also how on the reverse side of things, if you're not faster than it, it will be able to leave a big dent in you regadless). Similar applies to Syclant, leaving Pyroak. But even negating that and assuming it wouldn't be able to touch Syclant and Weavile at all otherwise, that means you're adding on several weaknesses just to make it handle three Pokemon (Syclant, Pyroak, and Weavile) more easily, and I'm not sure if that's a fair trade off.