At the midway point of the season, the Miami Heat is still not where it wants to be. But the Heat also doesn’t know what it can be yet. That’s because there’s still a sense of mystery surrounding the Heat despite its established core, as it continues to deal with injury issues that have led Miami to start 15 different players and use 22 different starting lineups. The only NBA team that has gone through more different starting units than the Heat this season is the Dallas Mavericks at 24. This caveat makes the Heat’s 24-17 record at the midway point of the 82-game schedule look better than it …