You are certainly the poster child for this problem.
Concerning your entirely conservative usage, here are some things that I know contribute to Other:
1. Safari history, certificates, cookies, and cache take space in Other. If you clear all of these, you should see some recovery, but of course that's highly inconvenient.
2. I'm not certain to what extent or for what purposes Mail uses other, but I would be surprised if this didn't contribute something. Perhaps attachments take up space.
3. Photos and videos in your Camera Roll or other Albums don't figure in Other, but it's likely that any editing that you may have done (and even cancelled) takes up a bit of space. This shouldn't be significant, I think, but people have reported that failed (and perhaps even successful) sync's can take up a lot of space.
4. You didn't mention whether you send/receive messages with photos or videos. These take up space in Other, and can account for a lot of space. As with Safari history, you may not really want to be clearing this out. I believe that phone and voicemail history also contribute to Other, but don't know how much.
In short, Other is used by the system and apps for many purposes, and no single method to clean it out will handle every person's usage patterns, which is why you hear so many reports of something that worked for one person having little benefit for others.
Until or unless Apple figures out what to do about this (assuming that they even want to), the only "solution" is to severely curtail your use while doing frequent "clean-ups" (whichever you find help), or to buy a device with more memory.
I'm currently on a 128GB iPad, and Other just keeps filling up. Soon, I will be asking Apple when they will be offering a 1TB iPad, for which I will probably pay $2,000. It's pure genius. Speaking of which, most people I've talked to, upon visiting a Genius Bar to help resolve the problem, are told stuff like "we've never seen this before". Which I personally find utterly hysterical.