No one can believe how powerful prayer is and what it can effect, except those who have learned it by experience. Whenever I have prayed earnestly, I have been heard and have obtained more than I prayed for. God sometimes delays, but He always comes.
Wherever the Gospel is preached, no matter how crudely, there are bound to be results.
Prayer, like faith, obtains promises, enlarges their operation, and adds to the measure of their results.
Righteousness and faith certainly are instrumental in healing the sick, deaf, or lame - if such healing accomplishes God's purposes and is in accordance with His will. Thus, even with strong faith, many mountains will not be moved. And not all of the sick and infirm will be healed.
It's wrong to try and convert tribal societies. What should the empirical evidence for religion be? It should produce peaceful, strong, secure people who are right with God and right with the world. I don't see that evidence very often.
And when you pray to God regularly, irregular things happen on a regular basis.
Faith no doubt moves mountains, but not necessarily to where we want them.
For many, religion has to do with what we are allowed to do and not allowed to do. In the end, that doesn't bear fruit.
Offended people still may experience miracles, words of utterance, strong preaching, and healing in their lives. But these are gifts of the Spirit, not fruits. We will be judged according to fruit, not gifting. A gift is given. Fruit is cultivated.