I voted no, it's not a DEM, for all of the reasons already mentioned.
As far as "writing themselves into a corner" -- this assertion makes no sense since pencils have erasers on them. They could have just as easily, as has been previously mentioned, had Rom disable the weapons one second earlier.
Look at "What You Leave Behind". The series finale originally featured a massive battle over Cardassia (it was late enough in the production process that this battle was included in the novelization) yet this battle was completeliy omitted in the aired version, reportedly for budget reasons.