I've yet to make up my mind or even understand this doctrine...and even if I came to believe every aspect of it, I wouldn't be too dogmatic about it. I am done with dogma…as long as a Christian believes Jesus is God's Son that would be what I would hold as more important than the finer points of what his godhood means. Even more weighty: following Christ's teachings in one's daily life. The rest, to me, is a tenth of the mint and the dill and the cumin.
But in regard to the Gospel of Luke, if we turn two chapters to Luke 10:18: 'Jesus said to him: “Why do you call me good? Nobody is good, except one, God.'
So whereas, one might use Luke 8:39 to prove that Jesus is God Almighty, some might use Luke 10:18 to prove that Jesus is not God Almighty.
Of course, people in both camps might end up disregarding everything Jesus taught between those two verses, and for that matter, before and after these verses. The most important thing about Luke 8:26-39, is what can we learn from our Exemplar in this account with the demon-possessed man--how can we do the same toward others in our daily life?