An alcoholic preacher witnesses abnormal behavior from his neighbors and must reclaim the faith he lost to battle dark spirits and the urge…to kill.

I would keep the job and the character flaw (alcoholism) in the logline. Also the fact that he has to fight the urge to kill is a good point. However we need to have two extra information in the logline. First what is the threat and if supernatural where does it come from. Secondly what does the preacher do to combat that threat.

Does it really matter what their jobs are, and their vice/state of mind? Also, I'd keep the mystery about the whispers as secret for as long as possible since most will assume they are from ghosts/spirits.

"Two neighbors find their small town becoming increasingly homicidal when eerie whispers are heard during the night"