Hi, Paladin21,
No, the Word of Faith movement doesn't believe that the person that has a disease has sinned and the disease is a result of that person's sin. What I have come to believe as I keep studying is that because we live in a world cursed by sin, we are subjected to that sin while we live in this world. (An attack of our fleshly bodies).
The only thing different from most denominational thoughts (and I go to an Assembly of God church) is that God gave us the tools to overcome this world of sin in the Bible. 1 Jn5:4. For whatsoever is born of God overcometh the world: and this is the victory that overcometh the world, even our faith.
God gave us all the measure of faith. We are all capable of having great faith as Abraham, Peter, Paul, etc. in the Bible because God is no respector of persons. We must use that faith put that faith into action. Our faith grows as we mature as Christians. The way our faith grows is by hearing the word of God and getting it into our spirit, not just memorizing it and giving it lip service and then speaking it to our mountains. It's like when we get saved. We believe in our hearts (spirit) and confess it (speak it aloud) with our mouths. Jesus spoke God's word to satan during His time of temptation (Mat 4), shows us how to come against satan in our own lives.
Quoting from Smith Wigglesworth in Ever Increasing Faith "Faith is just the open door through which the Lord comes. Do not say, I was saved by faith or I was healed by faith. Faith does not save and heal. God saves and heals through that open door. You believe, and the power of Christ comes." "The power of God is just the same today as it was in the past. Men need to be taken back to the old paths, to the old-time faith, to believing God's Word and every "Thus says the Lord" in it. " The Word of Faith movement, IMO, is just going back to those old paths and literally believing "If God said it, it's true and it's for us."
Unfortunately, when you mention faith (or the lack thereof) even in general terms, people start getting defensive because this goes to the core of their beliefs. But even Jesus had to chide His disciples for their lack of faith. (Mat 8:26, Mat 14:31, Mat 17:20) We can only look inside our hearts and judge ourselves and how much of the measure of faith that God has given us we are using, it is not for us to judge another person's heart. That's between God and them.
I hope this answered your questions. If not, please let me know.
Your sister in Christ
Chris