Full-text search without limitations (ignoring short/common words) on a forum this size would bring this site to its knees, as far as computation and storage goes.
We have the search index parameters at the recommended settings for a forum this size, and they are not going to change.
We know the search isn't the optimal experience we'd like - it affects the staff, too - but it's what we have and is going to remain as it is for the forseeable future.