Honestly, if he had really spent time with Kobe, he would have learned how to dribble, and wouldn't pass so damned much.
If I had to guess, the issue wasn't with Irving and Tatum (two Duke guys, btw, Coach K would have jumped in on that real quick). I think it was more Irving and Rosier.
For $30 million/yr, isn't Al Horford supposed to be a veteran leader? He's the oldest guy on the team. He can't say anything to anyone to clear it up? Then again, that goes back to the coach, because in the end, it's /his/ job. That's an NBA coach's job now.
Edit: More on the Tatum and dribbling issue. Last year it was 'fine', subpar, but not egregious. This year, teams had film on him, and were constantly poking at the ball when he got it. The only time he ever put the ball on the floor is when he was uncovered.