I've found that using advanced search with a tag plus a word works well enough for me, BUT the tag has to be a single word! I guess with multiple words its little brain gets scrambled and doesn't recognize that the multiple words are a tag.
A multi-word tag works perfectly well in other settings -- you can use it as a filter or in advanced search -- but it doesn't play well with others..
I'm a lawyer and use tags to identify broad subjects for quotations from cases etc. I have a tag called Statements of Decision, which combined with a word returned zero results. But when I renamed the tag to StatementsOfDecision (it doesn't have to have capitals), it worked fine.
Example: tag:Statements of Decision interrogatories -- no results
But: tag:statementsofdecision interrogatories - the two entries I have under that tag.
Using the filter would be much easier -- but at least I can get the job done!