Not sure introducing a Saab 2000 is putting the clock back 20 years - maybe 10!!
Seriously, turboprop aircraft are considerably cheaper to operate on short sectors than regional jets. Inside they are as comfortable as regional jets so what's the problem? FlyBe have shown it can work as have other airlines throughout Europe. So if Duo are struggling to make money on some shorter routes with their CRJs why not look at a cheaper option? It all comes down to costs and revenues at the end of the day and if you can minimise the former you should increase your profits!!