I think you guys are missing the point. The professional way to use UE4 (i.e not just use it as a learn-how-to-make-games tool) is to lay out the entire game logic as a set of C++ classes based on solid programming principles. Then expose tweakable aspects to Blueprint where level designers can rapidly tweak the behavior using familiar UI widgets generated by the BP. You now get the speed and robustness of a solid programming language (C++11/14) which has stood the test of time and also the tweakability of a high level visual scripting language. This c++/BP combo beats anything that is out there. Period.
Comparing just the BP bit to C# etc makes no sense. It doesnt exist in isolation and should not be viewed as such. If you cannot fully exploit the C++/Blueprint nexus then UE4 is not for you.