Think you should be careful to qualify this. It depends on how you're flying. Last time I did this, it was 17 minutes from my office to the gate traveling J with an ABTC card. 12 minutes taxi to the airport and 5 minutes to get through check-in, immigration, security and walk to the gate. It's never taken me more than 30 minutes total time or more than 10 minutes total for check-in, security and immigration.

If you're flying Y or an LCC, definitely heed the OP's advice. If not, SGN is a very efficient airport for departures. (Note however fast track outbound immigration is only available for Sky Team and ABTC holders.)

As for traffic, as the OP said, budget at least an 60 minutes during rush hour from D1 to the airport (I've walked in the opposite direction in 1 hr 20 min). Road construction at the airport is finished, so if you're on the airport side of D1 (e.g. D3) it shouldn't take more than 35 or 40 minutes even during rush hour.