When the video opens we see the aft cargo door already open with baggage carts in place, cones had already been placed forward of the wings and rear steps positioned close to the a/c. This indicates that the beacon had been switched off (safe to approach a/c) for at least a couple of minutes when the crew became aware of a fire.
Nothing ever happens like it does in the sim. Cabin crew are trained only to use exits and deploy slides where it is visually clear of obstructions outside and free of hazard such as fire. It appears as if the deployment areas of both rear slides at doors 2L+R were blocked by ground equipment so were not used by the crew.
With all the pax standing up in the cabin ready to get off I am not surprised everyone ignored the overwing exits.... the pax would have been in the mindset of going forward or aft to make a normal exit, and no crew would be by the overwings on the ground. The doors would have already been put to manual so all escape slides would be in the wrong config.
This seems to be and after-shutdown fire at the most awkward of moments with everything and everybody in the wrong place.
Perhaps you should devote some thought to how you would best managed it?