How to counter the mortars blind sninja

I have learned from experience that the mortar is a great building but however it has one big weakness, it's blind sninja. I have found a way to counter it, by placing a wizard tower next to each one. This way once the troops get into the blind sninja(after taking a beating from the mortar) the wizard tower will attack them with its strong splash damage effectively ninjaing of the hord of attacking troops!