There's a thread around here that can help you.
I use 10 speed Chorus shifters with a 9 speed Chorus RD to shift 10 speed Shimano.
I believe this is the only Campagnolo combination that will shift 10 speed Shimano(without shift mate). Oh, doesn't have to be Chorus, just 10 speed shifter and 9 or 8 speed derailleur.
RD is not brain dead as you say. I think the geometry and throw or something makes a difference.
Shifter/RD interaction is matched and some combinations will not work properly.
A good example is 10 speed 4700 Tiagra will only work with a 4700 RD. Part of it is the indexing of the shifter, the other part is how the RD moves in relation to the indexing.
For your application I think any 10 speed Shimano RD should work. Except for the Tigra 4700.
Campag will not work due to the difference in cable pull from shifter.