do you need one, I would say no you do not have to have one
would it be better to have one, I would say yes.
one to study under will speed up the learning proces I believe but then again you will never learn faster then you are ready. Correct me if I am wrong but yoga teaches us that we are what we need and all we need is ourselves? what is a guru? I have a hard time finding yoga people in person who can answer many of my questions, so I turn to books and find many answers. I ask on here and get some answers. everyone in existence is your teacher if you know how to learn from them. People see a "bum" on the streets, what can be learned from that "bum"? Also, different people have different streghts. a lady I work with talks of her meditation and I learn from here. My yoga teacher is largely focused on asanas and contemplation, I have friends who know some things about diet, etc.... So with multiple people, each specializing in a few areas, I can cover all the limbs and branches.
yoga also like non attachment, needing something is attachment. What if I have a guru and want to move, should I worry that I will not find myself? Also, a lot of people have egos and sometimes teachers get upset if you stray from their teachings. worrying about answering to someone, a guru, might hinder someone. I met a guy who grew up in a buhdist monestarty untill he was 16, he talked about levetation being commmon where he was from and e had spiritual conversations with everyone I saw him meet. It was an interesting experience. He was very "yogic" in many things he did but he also, to me, seemed to justify and not answer to his things that he did that were kind of non yogic and used his knowledge to justify to others. If you went by his teachings and tried to adapt all of them, you may end up witht he same flaws.
If you have a guru do you look up to that person? anytime you place someone higher then yourself you set them up to fall down at the first sign of a flaw. People see Jesus as being pure, well that if they though he had sex with woman, would that make him fall in their eyes? I do not see people such a jesus, buhda, ghandi, etc.... as being greater then myself. I see us all as equals. Jesus said soemthing like, "these things I do you shall do and greater" not an exact quote but kind of th point of it.
do you need a guru? everyone and everything is your guru!
the question is a tough one because it is not black and white. Personally i would want to surround myself with aware spiritual beings, but do I need to have that or I will not find myself, a lot to think about.
thanks for asking the question, it was fun to think about.
enjoy the journey