You're not looking at this the right way.
Hurley started reducing Gaff's minutes because he wasn't playing well and STILL didn't increase Diggins' minutes. Diggins' minutes were what they were because of how he was practicing and performing, clearly. Because there was no relationship between Gaff's minutes and Diggins'. And now that Cole is gone and there are a ton of minutes available, Diggins isn't sticking around. Maybe the relationship is fractured, but Hurley isn't a fool. Hurley is a PG himself. He's not fracturing a relationship with his PG of the future to play a guy that he himself was benching quickly.
Barely. Gaffney was down to 4-8 minutes a game by the end of the year. If Diggins could do anything he would have been playing. There's no doubt of that.