Scorer?
universally: athleticism + speed + Offensive IQ are necessary for any position to score. For big guys, in the new engine it appears low post is by far the biggest factor, but rebounding also helps put the offensive board back in. Also, a PF with decent perimeter can really dominate. For guards its superior speed + decent BH and acceptable perimeter (passing is necessary too, but not for scoring). I haven't seen the new engine really hurt any guards with poor LP skills. For small forwards, good speed + above average perimeter and low post, along with decent ball handling will produce.
3 Pt Shooter?
speed + perimeter + Offensive IQ. A player without speed will never get open enough to get a good look and obviously a player without perimeter will never make the shot no matter how open.
Assist maniac?
passing + speed + Offensive IQ. In HD, speed also means quickness (yes I know that seems like it should be athleticism, but Seble/developers have stated otherwise) and a player cant be a great passer without quickness to get that pass off, and the passing skills to get it there.
In other words, what in the WORLD makes an Offense FLOW in HD?
1) Know the offense you are running, and what makes it work. Know what individual skill sets make your particular offense work. For example, I know in the triangle, I need a big man with good LP and a SG who can catch and shoot. There's a full article pinned at the top of the forums about the offenses run in HD.
2) Proper team and player game-planning. Use exhibition games to find who the best scorers on your team are, or experiment a bit moving the distribution around until you find something that works; when you find the right formula, you will know. Exploiting game-to-game match-ups via offensive distribution or defensive positioning can make or break a game.
Also, don't always feel the need to play someone at their assigned position. This season I am doing fine starting 2 SG, 1 SF and 2 C. If you have a speedy C/PF with decent perimeter, some teams can even fit him into the SF position.
But no matter how good a player/recruit looks, always remember defense, especially in this new engine where individual match-ups can be more exploited. Even in a zone, a poor or slow defender can weigh your team down. In this game, offense is obviously not everything. There are many teams that win by shutting down the other team defensively.