Sorry for the late reply, I've been out for a few days.
Right now there's no real impetus to create new action items from this report. The purpose of gathering the data wasn't to generate this specific report; that was just a nice incidental benefit. Obviously if in the future we run into problems supporting the volume of regex queries that we are getting, we now know that there's a good chance that we could have a major impact on that volume by tracking down the source of these three regex patterns and finding out what they are trying to do and help them to do it more efficiently (or throttle them if necessary, though hopefully it wouldn't come to that).
We seem to be doing okay at the moment because all these biggest users are using queries that are reasonably efficient because they contain either non-regex parts (like "LOC" or the full URL) or have some decent stretch of literal text in them (like "[[en:") so we can use "trigram acceleration"—that is, search first finds documents with character trigram literals from the regex—and then performs the regex search over non-regex/trigram results. This can cut down the pool of potential document from millions to a few thousand, which is much more manageable.
—Trey