sickness and disease?
Why blame a demon? These are part of life. Eating better and excercising more will help. Genetics has a role in this too. God healing is not removing a demon, it is his grace and mercy.
>not all believers have the indwelling of the Holy Spirit
They are not his if no Holy Spirit, and I am not insisting on tongues.
Rom 8:9 But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his.
> they will cast out demons
Demons are in the way of salvation, they oppose God. Still the person can be reached by the word. I have cast out demons over the Internet of one seeking God, there was someone with her helping me. She was thrown to the ground, the possessed girl through up and left the house. Several days later she returned and we led her to the Lord. She now is active in a church and has a home for others coming out of bondage,
You work in the body of Christ casting out demons?
Not all are really saved, though they are with us.
Mark 1:23 And there was in their synagogue a man with an unclean spirit; and he cried out,
Mark 1:24 Saying, Let us alone; what have we to do with thee, thou Jesus of Nazareth? art thou come to destroy us? I know thee who thou art, the Holy One of God.
Mark 1:25 And Jesus rebuked him, saying, Hold thy peace, and come out of him.
Mark 1:26 And when the unclean spirit had torn him, and cried with a loud voice, he came out of him.
Mark 1:27 And they were all amazed, insomuch that they questioned among themselves, saying, What thing is this? what new doctrine is this? for with authority commandeth he even the unclean spirits, and they do obey him.
This may be your ministry, cleansing the church of demons. Not all within the church are truly born of God. One recent survey said that only 9% in church believe as the Bible teaches.
Beware of demon removal where the are not willing to put Jesus and His Spirit in the vacancy.
Mat 12:43 When the unclean spirit is gone out of a man, he walketh through dry places, seeking rest, and findeth none.
Mat 12:44 Then he saith, I will return into my house from whence I came out; and when he is come, he findeth it empty, swept, and garnished.
Mat 12:45 Then goeth he, and taketh with himself seven other spirits more wicked than himself, and they enter in and dwell there: and the last state of that man is worse than the first. Even so shall it be also unto this wicked generation.
This casting out of demons must be in the process of the soul seeking Jesus.