The icu DLLs are in my Qt 5.5 distribution, they are not in the Qt 5.6 distribution, so apparently your reading is correct. This is true for both MSVC2013 and MSVC2015 Qt distributions.

- Are you building everything in 64-bit mode (the error message refers to a library in a "win64" directory)?

- Are you building and linking everything in either Release or Debug modes? You cannot mix-and-match in Windows.

- Were the Matlab DLLs built using VS2015? Try switching your own build to use the VS 2013 platform toolset. (Properties->Configuration->General in VS2015)

- Install Qt 5.5 and try the build from that. You can have multiple Qt distributions installed. Tell VS which one to use from the Qt5 plugin options and project settings. You'll also need to adjust your PATH to load the right DLLs at runtime.