I would assume the vast majority of questions on this site will have to do in some way with the translation of a word or phrase from English to Spanish or vice versa. Should we tag all these questions translation? Or is that tag too broad?
I disagree that most questions are about translation. Most questions are about usage.
Often, but not always, questions involve a comparison with English or another language. That doesn't make them translation questions.
The good translation questions here are the ones specifically asking how to map an idiomatic or colloquial phrase or possibly a rare word to the other language. The kinds of things that are either not in typical dictionaries or are sometimes just hard to find in them.
Those are the ones that should have the "translation" tag. Remember tags are about "how to characterise a question". Things that come up in a question as sidenotes or background etc do not characterise them. "How do I say 'foobar' in Spanish?" however would be charterised by the "translation" tag.
Well first of all I don't think that the vast majority of questions will be related to translation. Depends on what you interpret as translation. For me it is A = B. But by another definition the site being in English then all questions are about translation.
There are many more questions that treat spelling, grammar and word specific issues related to Spanish. The site is more dedicated to those questions rather to brute translation. Only when the translation is tricky and the question is valid for the site should the question be with the translation.
The tag is not broad as long as the question is specific and not too localized at the same time about a translation subject that requires a native or experienced speaker's answer...
That's how I see it