CSK probably want to replace Bravo, the batsman rather than Bravo, the bowler. And the decision to take D Hussey is sensible in that aspect. And D Hussey is also a useful spinner who can easily bowl his 4 overs out.
But if we have to play D Hussey, we cant play any overseas fast bowler since Smith/Baz/Faf are certainties that cannot be replaced. So I dont see the point in picking D Hussey. We should have gone for a fast bowling allrounder in the line of Bravo.