It's very important to know what it is about your workplace that bugs you and look for an employer that doesn't exhibit them.

I wonder, however, how likely the questions are to work. I'm inclined to think you're more likely to get a positive response regardless of whether the situation is truly positive or not, because companies are so worried about positive image. The last company I worked for would have said just about anything to make themselves look good, while the whole company was really the fifth circle of Hell. 

I think having the chance to talk to potential coworkers would be great, and you're much more likley to get a straight answer out of them, as long as they don't think management is going to find out what they say. I think I'd go for a bit more of the direct approach, so they know what you're asking; they may not necessarily associate "psycho boss" with "process improvement." Perhaps asking "What is the relationship between managers and employees like?" would be a bit more direct and likely to get a straight answer.