VRs are overpowered period. In the beginning, you can go reactor core and pump out marines to fend it off. But if they can micro well, once they get like 7-8, you cant do shit. Fully charged VRs rape the crap out of vikings. and then by that time, marines and just pew pew pew. There is no other anti air worth mentioning. Thor? Maybe with the splash damage? But VR's dps is too high and will kill it. I think Thor does 8 + 8(light). I dont think VR is light but correct me if i'm wrong.

Reaper rush is good but it loses its effectiveness really quickly. Once a stalker is out, no more reaper. And 2-3 marines can fend it off easy. I don't like it because its so gas intensive. 50 gas so early on is a lot yo.

Even in high level play MMM is a strong build. Of course it depends what race you play with. I see a lot of ppl experimenting with Viking, Tank and Marines build which i find pretty cool. I think hellions and rauds are pretty effective against Z. But I'm bored of the game. Too much effort to get good lol.