I wonder what does sabotaging the cure accomplish? So the genophage still stays in effect? In that case krogans are not that big of a buff for the war effort. Their numbers are a key to their strength.
First off the cure seemingly is only on Tuchunka. Also since the shroud is blowing up one might be able to say that it only worked once. So the cure isn't STILL in the air, it was a one-shot chump. So only krogan on tuchunka during the cure dispersal are cured. Even if all Krogan in the galaxy were cured instantly, so what?
What does sabotage accomplish? The salarians. The salarian fleets. The salarian's have some of the most cutting-edge, high-tech ships in the galaxy. We're fighting /reapers/ which are giant sentient starships. Even if we had hundreds of worlds filled to the brim with krogan they can't do much against the reapers. Great for protecting the surface from ground troops but the reapers could bombard them from space. The krogan don't have any kind of fleet.
What does the cure accomplish? It makes Wrex happy. Sure, it does wonders AFTER the war but nothing for it right then. The reaper war didn't even last a year. Even if all the Krogan popped out babies on day one they'd only be a year old. Their numbers rise fast but it takes time for an infant to grow into to a warrior. Ultimately the actual cure did /nothing/ for the war effort. Though, in fairness, this is from a player perspective. Had the war lasted as long as the prothean (generations) the krogan birthrate would had helped.
Also, just as a quick clarification I'm not really against the genophage being cured. I just think it should had been regulated. Is giving the cure to krogan like clan Weyrloc really the wisest of moves? There are a lot of krogan that hold a grudge and would want revenge. I don't think ALL krogan should be cured just because Wrex happens to be not-so-terrible or because Eve is peaceful. Imagine the horror if this cure makes them immune to Genophage V2. Next time our only way of stopping the krogan would be flat out genocide.