I think prophets have to be natural leaders because of the office. A prophet naturally has to be a peacemaker, rather then a peace keeper, because they have to go tell it like it is. If they were not leaders, they would not be able to do that. I know what you mean as far as not in a position, but as far as an attribute, excellent quality.
Yes. I would say they were all leaders. A man in his own home has the responsibility of acting as a leader, a pastor is a leader, a worship leader is a ... well, a leader. Authorities in our society are leaders. Parents are leaders.
When you are leading people with the instruction of God's word, you are being a leader, whether or not anyone likes it. You are leading them to the truth. Whether or not you're spending a lot of time laying on your side for over a year eating bread made from beans and pulses (Ezekiel 4), or hiding your underwear under a rock (Jeremiah 13) , or preaching naked (Isaiah 20), or the most important leader of all, getting kicked out of town because you sent demons into all of their pigs. (Mark 5)
But we also have Proverbs 16:32 "Better a patient person than a warrior, one with self-control than one who takes a city." David seemed pretty chilled out but it was the spirit of God that was with him that made him successful in going out and bringing back a box of a couple hundred you-know-whats, which is pretty gruesome in my opinion. I believe that it was the Lord that gave him his strength. (Have you ever just had the courage rise up in you to where you knew to do something at the right time and you didn't really know where it came from?)
There's a lot of gruesome in there. There's a reason they don't finish the story of David and Goliath in Sunday school.