I have travelled Joo Chiat many times, I don't see an issue. 16
is doing fine with SDs. It doesn't need DDs.
Bedok - Marine Terrace (20-30 pax loading, also have 196)
Marine Terrace - Joo Chiat (30-40 pax)
Joo Chiat - Dakota (this is where loading reaches around 70 pax,
also have svc 33 that happens to be svc 33 high loading sector as
well)
Dakota - Orchard (between 40-50 pax)
Orchard - Tiong Bahru (between 30-50 pax)
Tiong Bahru - Bukit Merah (30-50 pax)
So apart from 2 stops along Dunman road, where there might be
difficulty to board svc 16, the route currently is strictly SD
loading and hence DDs don't really make sense. But can always give
2-3 DDs to start with and see!!
16 and 33 cover different parts of Joo Chiat.