I disagree that faith is needed for bhakti. Although you will see in some translations the word "Shradda" translated as faith, that is actually a mistranslation, the word actually means steadfastnesss and connotes a conviction born our of ones reasoning and discernment.
There is no place for faith in dharmic culture, dharmic culture is scientific, it demands evidence, this is why I object to the usual rendering of dharmic religions as "faith" There are some ignorant people who treat dharmic religions as faith, and they are the ones you find engaging in bizarre rituals, superstitions and generally they are stupid.
Yoga doesn't make you stupid, it makes you wise and discerning, it sharpens your intellect and every other cognitive faculty, it awakens genius. To do Yoga the less beliefs you have the better. Now why would you do Yoga in the first place if you did not believe in the metaphysical entities of Yoga: Purusha, Prakriti and moksha? You don't believe in them, you know them, though your practice of Jnana, self-inquiry, reasoning and scientific analysis you become aware of these metaphysical entities. When your reasoning reaches a level of indubitably, conviction is born and from that bhakti. Then you start your practice. If there are still doubts remaining when you start practice, you need to go back to the drawing board and see whether you have truly understood the metaphysics behind it.
There is an obvious distinction between belief and knowledge. I only say I believe something when I do not know it. I don't say "I believe I am typing to nobody right now" I am typing to you right now. This is verdicial knowledge validated by my perception and there is no doubt at all in my mind. In science, it works the same way, after having validated out findings repeatedly we develop conviction. An extreme example of this is the science television show "Brainiacs" They people on this show put to test scientific laws by putting their lives at stake, if the law is wrong, they're dead. Fortunately, nobody has yet died on the show Such conviction is born from Jnana.
Don't pretend that you don't know anything - you are throwing the baby out with the bathwater with this feigning of humility. What you should say is you know somethings, but your knowledge is incomplete. In Yoga we do recognize something called "valid knowledge" Valid knowledge is distinct from fallacious and imaginary knowledge, while valid knowledge corresponds to an actual real object to know, the latter do not correspond to an actual real object, either because one has misprehended the object and formed wrong knowledge or because it's imaginary(like the hare's horns) Valid knowledge is our starting point to get to the ultimate natural knowledge that comes through Yoga. This is why Patanjali mentions several stages of samadhi - beginning with ordinary analytical knowledge.