Why do so few light novels make it over via timely translation?
Light Novels are indeed harder to translate, but that isn't the real cause for their delay. The market for LN is really small outside Japan for a number of reasons so companies aren't interested in publishing them unless they are for very famous franchises (like Haruhi), and even then it's very risky.

As I said, translations and edition arent the reason per se, but that also affects. Translations in sites like Baka-Tsuki, while being done with lots of effort and having lots of stages for correction and quality check, doesn't quite fit the quality expected for a commercial release. Even in Baka-Tsuki the translations takes lots of time to be published, corrected and polished, so you can imagine how long that would take for a commercial-quality release.