There are several kinds of insomnia. In my case, getting to sleep is seldom a problem (and when it is, it's indeed often if not most often that kind of "thinking too much"), waking up too early is the big one. So, besides this being a generic disorder (my uncle the engineer followed the same path as I at the same times in our lives, but he's frankly bipolar with anxiety being of less significance), the effects of Seroquel on dopamine are not much if anything of an issue for me. Then again I'm taking a low dose of it (50-100 mg in one dose before bed, therapeutic dose of it for its formal indications don't go below 300 mg/day).
One thing to emphasize from our disparate experiences is that in this arena there aren't "one size fits all" solutions. There are common symptoms which respond to common solutions, sometimes after a search for a particular drug that works with acceptable side effects, then there are people like me where doctors and myself struggle for years to find a set of drugs that provide the best solution (for now) that control but by no means cure my symptoms (like my uncle, this eventually disabled me).
Getting back to the original basis of this discussion, I'm absolutely sure that Amblify when used as an adjunct for current generation antidepressants works from some people with refractory depression, which I can attest is no fun at all, since mine is only partially alleviated, and I have friends who spent years before they found at minimum partial solutions for their more standard unipolar depression. Is it seriously over-prescribed? Who knows? In my experience, there are enough people out there with refractory depression that it might well not be. And I'd certainly try it before e.g. electroshock therapy, which is one of the alternatives if you're desperate enough.
As a side note, I learned cognitive psychology in the '80s (now cognitive behavioral psychology, http://www.amazon.com/Feeling-Good-New-Mood-Therapy/dp/03808... is the classic and highly recommended layman's introduction), and it's tremendously useful, and in retrospect ended any benefits from talking therapy, but it's pretty clear that like the 3 particular antidepressants I've tried from two generations of them, only a partial solution for me.