Most checklists call for O2 masks if required. In this case the crew donned the masks when required. One thing for sure, as soon as the masks come on, the communication on the FD becomes alot harder, so I think good job.
As for the evacuation, with no obvious signs of fire from ATC, cabin crew, would a precautionary disembarkation have been a better option. Our procedures enable it to be done with or without steps/air bridge and minimises any injuries which may come about from an immediate evacuation and all the panic associated with that.
Either way, I think a good job to the entire crew, including the CC who first brought it to the attention of the FD.