You can't evaluate stats without context, pure and simple. And you can't cherry pick which stats you will and will not look at (disregarding fg%) - all of these numbers come without context. And as far as counting numbers go, 5 assist per game actually is pretty solid, esp if he's playing with guys who like to score off the dribble. The "can he run a team" question" is answered by more than the number of assists (see: Omar Cook's great assist numbers but so-so leadership/ pace setting skills).
I'd like to see some eye popping numbers, but what was it he averaged in high school in an earlier link? 31 points and 11 assists? I have no idea what either of those sets of numbers mean. I have more context for city HS ball, for example - Malik averaged something like 6 points per game his senior year at CTK, and that was a warning sign, since we knew he got a lot of time.
I don't know if Armstead's team gave more time to a sophomore scoring point. If it were me doing the evaluating, I would have to watch a few of his games and see how he gets into the flow. And if so many teams seemed to like him coming out of HS, why didn't he sign then?