The Genophage is harsh because the Krogan are harsh. The entire battle strategy of the Krogan is to throw bodies at the enemy and hope the enemy runs out of bullets before the Krogan run out of bodies. Their extremely high birthrate (1,000 births per year per female) is the Krogan weapon. The Genophage takes away that weapon.
The Genophage is seen as a sterility plague because it results in 999 out of 1,000 pregnancies ending in either miscarriage or still birth. But it still allows for 1 birth per year per female Krogan. Considering their natural life span is 1,000+ years, each female is still capable of having hundreds of children. A horrid fate, but one that they earned through their mindless slaughter across the galaxy during the Rebellions. They were not, and are not, interest in diplomacy. They only stopped because of the Genophage. No other reason. The Krogan define themselves by their body count. They murder their way up the social ladder. The Genophage is harsh because the Krogan are harsh.
Personally, the only way I would be comfortable with curing the Genophage is if the Krogan were immediately confined to their home world. The council would drop food and supplies when needed. Hold annual summits with representatives from each clan and council race to monitor their cultural development and when/if Krogan society has evolved (or atleast become less trigger happy) talks about rejoining galactic society can begin. But until the question of "Who gets the last bottle of Ryncol?" doesn't end with gunshots, the Krogan stay on Tuchanka.
Wrex is awesome sauce. And Grunt... well... who doesn't love them some Grunt? But the Krogan as a whole are too dangerous to be left to roam the galaxy unchecked. I want to believe Wrex and Bakara can keep the Krogan from seeking revenge, but the odds are not in their favor. Best option is kill Wrex on Virmir, destroy the cure data, and put on a show for Wreav. Regardless of your choice, the cure is created and can be used at a later date. Now is not the time.