It is worth noting that the purest form of fideism is often found in cults and false religions. But a leap of faith is always dishonoring to God who created us in his image with a rational soul. Rather, God usually expects that we investigate and see if, in fact, the claimed revelation we see is that of God or Baal. Faith is certain as Hebrews points out, because it is taking God at his Word, and God's existence and the truth of his Word has already been demonstrated abundantly to the reason. The reason then rationally takes its rest when it receives conclusive proof that the one speaking is God who cannot lie.
Faith is certain because it is founded on reason.
This struggle of faith is not the struggle of the rationality of the faith. The devils have passed the intellectual persuasion aspect of faith, and tremble. Rather the struggle of faith is the fiducial or trust aspect. This new heart is entirely the gift of God, and the struggle remains in the believer to trust God in the midst of trials. It was eminently rational for Job to understand that God was working all things together for his good.