Wrex always talked about how the Genophage psychologically defeated the Krogan, not biologically. I presumed what he meant was that the Krogan were so fractured as a species after believing they were "sterilized" that they could not organize a feasible future for themselves if they went to war.
In ME2, Wrex is preparing the Krogan to go to war with the Reapers, with his reforms being the sole unique factor. He never brings up a cure as any part of his plan.
Wrex basically touches on being unable to replenish their numbers if they went to war, but then this also includes conflicts between clans as well as external enemies.
It seems to me that Wrex's plan to bargain for the genophage cure in ME3 was one of opportunity. Wrex wouldn't really have much of a leg to stand on if he demanded a cure without knowing that a cure was actually in the works, so we can blame Mordin/Padok for giving him intel that set this into motion.
But really, from the krogan's position, the potential end of the galaxy is the perfect time to bargain, especially if they don't really think that their species will make it through to the end if left at the mercy of both the bioweapon and a relentless enemy like the reapers, so to that end I can't really fault them. From their perspective, I'd demand no less from the turians if they wanted cannon fodder.