Hello,
I was pleasantly surprised to find 59 each way from London to a fairly distant city in Eastern Germany, so I was well pleased, although of course, it might be a different story booking at the time I really want to go (in summer).
The stopover mechanism seemed to work quite well as well.
IME (mainly test booking, but over several years) you can fairly much rely on the 59 fare to almost anywhere in Germany using the 0625 ICE from Brussels and its counterpart back, and on the 0743 from Köln.