Well Ponting's reluctance to bowl Symonds has to be a result of health factors (actually it's probably just Ponting's captaincy which would suggest poor team structure and preparation in terms of establishing a settled attack), although Katich looks the far better option over Hussey, keeping the success of Hogg in mind, who is a fellow left-arm wrist spinner, and the nature of the pitch. Bangladesh have really crumbled here, although it has been a solid performance by the Australians.
EDIT: Bangla now dismissed under 200, with Symond's bagging two cheap wickets at the conclusion of the innings...