look, if they fix search they might have to stop using "Confluence; where information goes to die" as a tagline... so not an easy sell.

seriously though... default confluence search-as-you-type box is horrible, however sometimes (often ? always ?) there is a more traditional search endpoint available that seems to give better results. see if either of these works for you:

<your confluence domain>/dosearchsite.action

-or-

<your confluence domain>/search/searchv3.action