Part two of my recommendations:Wartburg
definitely worth a visit, an exception to my above castle-and-park-statementKassel
I enjoyed the waterworks, and it is certainly a major reason for the inscription. Apart from that, the best attraction is the Herkules monument. Be aware that the name 'Bergpark' is absolutely justified, I have some doubts that it's a great pleasure in January. And Kassel is 1.5 hours from Eisenach and about 2 hours from Eisleben.Luther
I liked Wittenberg better than Eisleben, both the Luther sites and the cityHalle
I presume that the Francke Foundation will not get the inscription, the architecture is not outstanding and its global impact on education is not that high. Halle has a nice old town centre and the State Museum of Prehistory is quite interesting , its most famous object is the Nebra Sky Dischttp://www.lda-lsa.de/en/nebra_sky_disc/Dessau Bauhaus
we share the passion for modern architecture, so I assume Bauhaus will be a highlight of your trip. I would recommend the guided tour to the Bauhaus Building, the tour leads you through rooms that are otherwise not accessible. The Master Houses are open to the public (some of them) with and without a guided tour. In 2014, the reconstruction of the two houses that were destroyed in WWII was completed, the intention was a 'new interpretation' not a reconstruction true to original. It will be interesting to read your review on that.
Of the non-WHS Bauhaus sites I can recommend the Kornhaus restaurant, the others are less impressive. The Laubenganghäuser are part of the T-list extension, the former Employment Office is of some interest (open on weekdays).http://www.kornhaus-dessau.de/http://www.bauhaus-dessau.de/visiting-the-bauhaus-buildings.htmlDessau Wörlitz
The Georgium Park is close to the Master Houses, but the best part of this WHS is the Wörlitz Park, 15 km east of DessauAccommodation in Dessau
I would agree with nfmungard that Dessau is empty and dull (well, it has two WHS and you can't have everything), Potsdam would be a better choice to spent the last evening (the Dutch Quarter is nice).
But if you decide to stay in Dessau, an option could be 'Sleeping like a Bauhausler', a bit austere but authentic:http://www.bauhaus-dessau.de/accommodation.htmlPotsdam
one of my favourite WHS in Germany (so maybe I like castles and parks?). My recommendations: Cecilienhof (famous for the Potsdam Conference in 1945) and the Einstein Tower (not open to the public)https://en.wikipedia.org/wiki/Einstein_TowerLeipzig
worth a visit, a lively city centre and a good nightlife. The Nikolaikirche is worth a visit, I like the interior and it's the symbol of the peaceful protest against the GDR government in 1989.
Hope that some comments are helpful, have a nice trip and – may the force be with you.