I believe most people have doubts. To say differently says we're not human.
Many or most Christian believers I know well would tell you they have no doubts. Are they liars (maybe just "misguided")? Are they arrogant?
Regardless, I think it's safe to say the martyrs had no doubts. And yes, I would argue such faith is inhuman. "For by grace you have been saved through faith; and that not of yourselves, it is the gift of God." (Eph. 2:8)
Not human, or in denial.