Unfortunately, preprocessing is a slippery slope, even if you discount the serious performance issues. For example, when you start recursively parsing header files, well, first you have to be able to find them, so that means the user really has to set up his include file path correctly. As we have learned from our C++ refactoring engine, which absolutely has to do full preprocessing and parsing in order to build a correct DOM, just setting up include paths is a heavy burden for most users who just want to spin it up and go.
Now, back to the original question. If you find problems with C++ tagging apart from the aforementioned limitation with respect "using" in header files, please put together a small, but complete, example and report the problem to support@slickedit.com. We are determined to be the best editor available for C/C++.