Is it a production system? If not, you could consider restoring from backup from just before the import. Jelena's right, there is no "undo" for transports -- you either go back to DEV and activate an older version of the objects, creating a new transport to undo the prior one, or you restore from backup.
A SPAU/SPDD transport could indeed potentially have a large number of objects, which would be onerous to revert, not to mention with lots of opportunities for mistakes. The other consideration is that it would -- temporarily -- undo the work you've done in DEV.
So, unless it's production, restore from backup is the best option.
Regards,
Matt