I agree, the german version of DOTT seemed so lazily made, that I never actually bothered playing this version for long. The mistranslations can be kind of embarassing for a professional product like this and the line delivery sounded as if the voice actors had been given almost no directions. Also, the voice-compression was horrible (or maybe the recordings themselves were of low quality?): everybody sounded as if they had a lisp.
Retranslating the text or parts of it as subtitles for the englisch audio-track and keeping the original german translation as an option for die-hard fans (maybe with a little warning text ;-) ) might be a good compromise. Personally, I prefer to play in english anyway, but a cleaned up script might be a good way to introduce a completely new german speaking audience to this classic.
Thinking back, it was pretty rare for games at the time to get a decent german translation (not to mention good voice acting, too). The first game that really stood out for me in terms of high quality localization was Curse Of Monkey Island , which was almost as good as the english original. (That game totally deserves a HD-remaster, too btw. :cheese: )