Hybridization rates are not static. What's more, hybrid mosquitoes would in no way be limited to mating with other hybrid mosquitoes.
Consider that this gene drive diminishes the female mosquito's ability to feed on blood. I'd expect it be possible that this would cause modified female mosquitoes to be maladapted in other ways. If modified female mosquitoes were to experience significant additional stress, the adult sex ratio in modified mosquitoes could shift dramatically toward an overbalance of modified males.
If this were to happen, don't you see how it could increase pressure on males to outbreed? E.g. if a large proportion of their natural mates were either dead or malnourished? Similarly, can you see how the same kind of situation might emerge for the hybrids, increasing the likelihood of backcrossing?
A gene drive that specifically disrupts the females' ability to survive seems like it would increase the likelihood of introgression, potentially by a lot.
This whole situation just strikes me as highly unpredictable, risky and poorly understood.