The hands should go back, the less unnecessary movement, the better. The harder the pitcher is throwing, the more mechanically correct the hitter needs to be to hit. A hitter that lunges, doesn't keep his hands back, hitches or has a pronounced uppercut will not hit at a consistent level. When evaluating hitters focus on tools, not statistics. You should scout tools not performance.
Statistic are good for evaluating weaknesses.
A hitter with a high strikeout and low walk total is swinging at too many bad pitches, unless corrected will never hit at a constant level. A hitter should be able to turn on a good fastball on the inside part of the pate. If he can't, he has little chance of becoming a good hitter, because pitchers must throw inside to be successful at the major league level. A hitter must be able to hit breaking pitches or he will not last at the major league or minor league level. Once word gets out about a hitters can't hit the breaking pitches, he will see nothing else until he learns to hit it.