The ONLY format that will work on a DVD, and that Encore will not transcode, is "MPEG-2 DVD". Your older versions of Encore would absolutely have been transcoding the H.264 source prior to burning the disc, no other possibility. Maybe the older versions show different messages or something so that it was not apparent what was happening. But Encore was never putting H.264 onto a DVD. MPEG-2 is the official DVD spec and there is no getting around that.
The preferred workflow is to export from Premiere as "MPEG-2 DVD", since no other format will work without transcoding. This produces two files, .m2v video and .wav audio. Import both into Encore. The video should not need transcoding and the audio will by default be converted to Dolby AC3 in Encore. The Build should take only a couple of minutes - audio transcodes very quickly.
When you choose "MPEG-2 DVD" as the compression format, you will also need to choose a "Preset", such as "NTSC DV Widescreen" or whatever is most suitable for the given source footage.
The bitrate will need to be looked at before encoding. There are bitrate calculators online, or try 560/minutes=bitrate (but not to exceed 8.0 for shorter programs). Example, 560/120=4.66 and I round to 4.5 for safety margin.
If you are starting with an HD source, check the "Max Render Quality" box in the export panel as this will increase the downscale quality from HD to SD.
Hope this helps out
I encoded a video in Adobe Premiere CS6. I used MPEG2-DVD. I imported it into Adobe Encore CS6. It did not transcode the video.