YES! But your reasoning is not completely useless. As I said, it can help you to identify fake ones but can never give you definitive proof on real ones for they are beyond the realm of logic. Not only your reasoning is useful, but also your heart. Saints reach to people by all means they find effective. To the intellectuals, they may give you a sounding argument. To the others, they touch their hearts.
Faith is always blind or at least partially blind until your spirit reaches the realm of Allah. That is why it is called "faith", which requires obedience without logical proof. Not because Saints want our complete obedience for their sake. It is because our reasoning could get in the way of truly reaching the realm of Allah. Just like a kid who attends the elementary school for the first time. Should the parents tell him to have a thorough debate with his teachers or should they just tell the kid to listen to the teachers, at least for now? As I said, having more questions doesn't always lead to more answers. Sometimes, they prevent you from getting closer to the truth. But we are not completely hopeless during the journey. Saints, as our guides, will let us know what signs to look for that mark progress. So the faith is not completely blind.
I love one prose from Kahlil Gibran's "On Love":
When you love you should not say, "God is in my heart," but rather, "I am in the heart of God."
And think not you can direct the course of love, for love, if it finds you worthy, directs your course.
The same attitude can be applied to Saints and Allah. Don't think you can direct the spiritual course towards Him. He will direct your course when He finds you worthy. That is faith.