Exactly.
I won't dive into the hand-eye coordination topic or even the argument of muscle mass versus mechanics as being more relevant in improving an athlete's performance, but I will echo WW's thoughts on confidence.
Confidence is everything. Just ask anyone coming off a hot streak or a cold streak. And in the case of taking a performance enhancing drug, one of the biggest benefits an athlete derives is confidence.
And this confidence factor is both psychological and physiological.
Psysiologically, steroids release the chemical testosterone in the body. And studies show that higher levels of testosterone in men has a direct correlation with the level of aggression and confidence in those men. If you want to be cliche, the sports world calls it more "heart". When an athlete competes with more aggression and confidence, he will outperform his natural level of performance and often times, outperform his teammates and competitors.
Psychologically, injesting or injecting a performance enhancer will translate to a different mindset for the athlete. It doesn't matter if performance enhancers affect hand-eye coordination or not. All that matters is what the athlete thinks. If the athlete thinks he is seeing the ball better, then he is seeing the ball better. If the athlete thinks his bat speed has dramatically increased, then his bat speed has increased. Perception is king. Perception is reality. Just ask any athlete who's been in the "zone" or who has experienced any state of ultra confidence in their game.
Solid post.