While there is frequently an AUDIO_TS folder on a DVD I do not think there is a requirement for the folder. The AUDIO_TS folder usually only has files in it when there are alternate audio tracks (ie. other languages) on the disc.
If your replicator can not work with what you have sent then find a different replicator.
The AUDIO_TS folder is used ONLY for DVD Audio disc's this is very different from Video DVD's with audio. Encore does not author DVDA discs. I believe that the folder (empty on all video discs) is part of the DVD standard, but players will play a disc without the folder present.