You could try using Final Cut Pro (not sure if Express encodes to MPEG-2). Or DVD Studio Pro. Both encode for DVD and are faster than Toast in my experience. Also, Toast has a horrible encoder. At least for me, I always have visible artifacting and even some glitches that cause discs to not play back properly. I would avoid Toast for DVD burning at this point unless it's truly a quick and dirty approach or something you don't care that much about. Admittedly, Toast is still the absolute easiest way to burn a DVD, even easier than iDVD.
I have found encoding times to be somewhere around twice real time for a single pass encode on a Dual G4 1 GHZ, 1 GIG ram. Or 4x real time for a two pass encode. So, on my box an hour long piece might take around two or four hours to encode. That's using higher quality settings. You can encode much faster by sacrificing quality, which you can change in either program.
Unfortunately, I don't think you can use just QuickTime pro to encode to MPEG-2.
You may want to try iDVD and see if it encodes faster. It's very possible. I have found Apple's applications to encode audio/video MUCH faster than other third party apps.