Most god def. guards seem to have average to good speed, which helps them on D. They usually aren't great offensive players, though, but I would expect that. I mean, if a guard is a good def. player and strong offensively, he is a special player. Of course there are some but just like RL they don't coma a dime a dozen.
In my experiance the better shot blockers do seem to be good rebounders, which makes sense. Size would make a player good in both of these areas. What I have a lot of trouble finding is a big man that can rebound, block shots AND put the ball in the hole, but again, that's to be expected.