Ah...now I have it.
Considering that most, if not all of the geniuses, including Einstein were dyslexic, the answer must be NO. It is not unusual.
What is unusual is a teacher able to teach a dyslexic. A dyslexic person is capable of learning from a teacher, if that teacher can impart the information in a manner which displays his/her holding a firm knowledge and understanding of their subject.
Return to Einstein. He was thrown out of school as being unteachable so he taught himself now scholars study his work. However, studying the work of a genius and learning to reproduce it in answer form on an examination paper, sufficiently as to attain a pass mark, does not signify true understanding of the genius's work.
Frequently, the "class fool" will be the brightest pupil but with a dyslexic learning pattern. It takes a good teacher or enthusiastic about learning educater to rid the dyslexic of the frustration they might feel when faced with the difficulties of dyslexia.
Dyslexic people often know they can learn what is being taught but their pattern of learning is such that they have to view the lesson from different angles then it "CLICKS". It may be merely one aspect of a lesson then they can surge ahead as they usually/often hold the key to drawing on information and self teaching/learning.
Without a good teacher, who can help and guide the dyslexic student through the process , applying much patience (a basic in the core of a good teacher), that student can turn to becoming the "class clown" to detract from what they feel to be a blocking embarrassment regarding their learning ability. Too often, due to the teacher's lack of ability, the dyslexic aspect of a student is not picked up upon. The student may be branded stupid, even, on occasion, ridiculed by the teacher. That is unbearable to a person who knows they can but are not given the opportunity to realise their full ability.
Guess, from this rant, who is dyslexic?
Apologies for the rant...not for being dyslexic. I consider that to be a mark of distinction.