The thought of having Kanter and Randle on the floor together, where both can hit from 20 feet, both can drive and get to the basket with body control, and both can score in the post would give the Jazz a nice 1-2 punch offensively. The same could probably be said with Parker and Wiggins, but Kanter and Randle could torture the other team's bigs all night, with one of them going hard on the offensive glass on every play.
Good teams like the Spurs and the Heat space out the floor and let their most athletic player break down the defense--Parker in SA's case, and Lebron normally for the Heat. The Lakers did this too, with shooters on the wing and Kobe going at his defender from the top of the key. Then if Kobe didn't convert, Lamar Odom was right behind looking to clean up. The Jazz have a really nice clean-up crew, with Kanter and Favors (and add Gobert), but they need that primary player who can break down the defense.
I feel like Parker is probably going to be a guy who floats mostly on the perimeter, like a Rudy Gay or Danny Granger. Although Parker is a triple-threat player (shoot, pass, drive), I'd like to have a guy whom I know can get a step, get into the lane and break the defense. I think Exum and the Harrisons might be just as effective as Parker in this respect. This is probably why Parker is sitting in the 5-7 range of most mock drafts right now.
BTW, Hayward is trying to play this role right now, and it's not really working.