My uneducated opinion is that Heyward hasn't been good. I stated that I am no hitting coach. I watch 90% of the games and cannot say with any certainty that he has hit over 20% of what I would consider line drives . If he is hitting that many that are truly line drives they must not have much on them or too much lift was what I said. The low "luck" factor and power shortage are likely related. In short he hasn't put up those numbers, so all this but and ifs dot mean squat. The numbers are what they are, and what he has contributed to the team and that's what counts.
In the end you can't argue that Heyward has been good at the plate so I'm not sure how I'm wrong. I am hard on Heyward because without him we go nowhere.