Yeah, the Salarians bungled the math pretty badly. ("Too many variables.") That doesn't mean the concept was untenable, merely that they dropped a decimal point somewhere.
Pity that when they had a chance to fix it, and by they I mean Mordin, they didn't look at the Krogan situation at all, merely concluding "1 in 1000? Yeah that's what we arrived at before, roll it forward and punch the clock so we can get off this dustball."
As far as Wrex and Eve, all I can heartily recommend is that we take Garrus' suggestion of getting them both a food-taster.