Yes, I believe in R2010b and earlier versions, the use of LCC to parse symbols is the default behavior of LOADLIBRARY. However, in R2011a, LOADLIBRARY started honoring the compiler chosen with "mex -setup". If you do not plan to upgrade, you can try first running the MSVC preprocessor on your header file to produce the corresponding .i file, and then provide that in place of the header to LOADLIBRARY, so that the preprocessor is not run.
You should be able to run the MSVC pre-processor on your header with this command from the Visual C++ command window:
cl myheader.h /P