My oldest DS is has rather severe Dyslexia and a totally normal processing speed on WISC. He was tested every three years and it really stayed fairly consistent from 6 to 18.
I would say processing speed during reading or writing task is slow, but on WISC testing it was average to high average over the years. I have never thought of processing speed as relating to dyslexia. It maybe related for some kids,but it wasn't in our experience.
I think daydreaming can be a lot of things and would not jump to ADD for that behavior alone. Executive functions such as organization, following more complex directions, and even daydreaming can be seen in both ADD kids and dyslexic kids. Many of the behaviors overlap in ADHD and Dyslexia.
