So everyone out safely - only just - and THEN the fire trucks roll up. Is this a little slow?
That depends on when they were called. I thought the evacuation requirements were to have everyone out in ninety seconds, at least on the certification test. No doubt with a real fire, the pax were incentivised to at least match that time. If the doors were opened about the time the call went out for the emergency response, I'd expect the evacuation to be complete before the trucks arrived unless they were based right next to the terminal. In general, I'd assume the positioning of the emergency vehicles building is more optimised for a fast, clear route to the runways as that's where they're more likely to be needed in a hurry.