" Three (four?) different studios worked on this, I somehow doubt it's a cohesive experience."
Don't worry about that 95%+ of this game was made by 3DR, but in May 2009 they fired the entire dev team for financial reasons. At that point they were planning to go gold on April 1, 2010(and would have made it according to Jason Bergman who was Take Two's Producer on the game back then). Shortly after the team was fired 9 of them started working on the game for free out of their own houses/apartments they worked out a deal with 3D Realms to be able to continue doing and and formed Triptych Games. By late 2009 Tripych had finished the singleplayer portion of the PC version. At around the same time Gearbox got involved in the project and bought the Duke IP. Gearbox has assisted Tripych with polishing the game, providing QA, Production, Engineering and Art resoursces. Gearbox assigned the Multiplayer as well as the PS3 port to Piranha Games, but the MP is build on 3DR/Triptych levels.
The Triptych website:
http://www.triptychgames.com/