1. God invites us to pray. We pray at His request. Prayer is not just asking for stuff, but the dialogue of the relationship. We talk to people we love.

2. All things are not determined (Jer. 18.1-12). It's not like God has a plan and there's nothing anyone or anything has to do to change that. It's all changeable except the plan of salvation. We are invited to pray to participate in what God is doing on the Earth and what God is doing in our lives.

3. God says that He changes things based on our prayers. James 5.16

4. Suffering doesn't happen because God is a perfect being. Suffering happens because we make bad choices, sin is a reality, and some people are evil people. Suffering also happens just in the course of natural cause and effect. God does work to redeem suffering and to bring good out of it. Prayer can be an important part of that picture.

5. Even though some people like to throw around the aphorism, "There's a purpose in everything," I'm not so sure about that. The Bible doesn't say it. And it certainly not true that God is making happen everything that happens. Most suffering is not God's doing, and He doesn't "have a purpose in it." He does work to, as much as is possible, turn it into strength, courage, love, cooperation, sympathy, and many other things, but God doesn't cause most of the suffering that happens.

6. Praying isn't necessarily asking God to change His plans. There's nothing that says every minute of our lives is planned. While God knows what is going to happen, we all know that knowledge isn't causative; only power is causative.

7. Praying is not questioning God and His plans. It is coming alongside of Him in this great adventure we call life.

Therefore, it is not reasonable to conclude what you have: "And would it even be reasonable to say that, if a prayer is made and the outcome is favorable to it, then the resulting situation either: a) is the perfect outcome and would have happened regardless (God's plan worked as intended), or b) is non-perfect and therefore in defiance of God's plan." This conclusion is in error. Feel free to talk more.

Disclaimer: I am atheist, and my understanding of theism is mostly drawn from personal research and the views of Christians I know personally, so some of the base assumptions here may be incorrect.

Why do people pray for divine intervention? E.g. "please heal my sick brother", "please help me cure my addiction", etc. As I understand it (based on the views of Christian friends), suffering happens primarily because God is a perfect being, and His motives are not always fathomable to us. However, being by definition both good and perfect, we have to accept that there is a good reason for such things.

This makes sense in its own way, but it does lead me to wonder: why pray for a change in those plans? Isn't that questioning God and His plans? And would it even be reasonable to say that, if a prayer is made and the outcome is favorable to it, then the resulting situation either: a) is the perfect outcome and would have happened regardless (God's plan worked as intended), or b) is non-perfect and therefore in defiance of God's plan.