I think he did a fairly good job and Brind'Amour said he wanted him back, but Dean wanted to see if he could get more money elsewhere. It's really hard to say though how much of an impact an assistant coach really has. When Brind'Amour was an assistant under Peters, probably nobody thought he was doing a great job.
Can't give too much insight on him specifically so it's hard to tell, but as far as how the Canes played defensively:
Canes play an aggressive style defense where they pinch aggressively to keep pucks in, have tight gaps in the neutral zone, and try to gain possession and move the puck up the ice quickly. While this is effective in driving play/possession, and helps the forwards in transition, it also puts a lot of pressure on the defensemen and there's little room for error. Most of the time, the defense with Hamilton, Slavin, Skjei and Pesce are mobile enough to recover, but when there is a breakdown, it often leads to a high danger chances. So while Carolina was good at preventing shots, they were average/below average at HDCA/60 because of how they play.
They also, as a team, weren't great when a team gets in on them and cycles, but part of that is many of the forwards aren't physical enough to win some of battles.
How much of that is how Brind'Amour wants them playing vs. Chynoweth's coaching? No clue.
