The thing with Ado is even if he gets the ball wide open under the basket, there's a 50/50 he will take so long handling the pass and getting the ball up that the other team will have time to recover and block his shot. WSU pretty much ignored him when they were on defense, except right around the rim.
But when Ado plays well, which happens some times, he is our best big. He has dominated on the offensive boards in a number games and played excellent defense. The problem is, he is so inconsistent (there are rumors of a lingering wrist/hand injury that may account for this). He's almost a guy you give 10 minutes in the first half and then sit him for the entire second half if he isn't playing well.
Koval/Ody are situational as well. They both struggle against bigs with size, especially Ody (who really struggles everywhere on defense). Koval is excellent against more mobile big men.
It comes down where do you want to be weak? Offense or defense? Miller generally prefers to be weak on offense. There really isn't a correct answer, but as long as Miller prefers guys who play defense over guys who play offense, Ody's minutes probably aren't going to increase and Ado's aren't going to decrease much. Koval might be earning more minutes though as he can excel on both ends in the right situation.
If you watched the post-game, Miller said at the end of the WSU game they talked about going offense/defense with Koval/Ado (same as they did against ECU), but he decided that Koval was their best option on both offense and defense against WSU's offense (they were running a lot of high ball screens, which Koval covers better than Ado).