Flashman,
You're dead right that the grip is the essential piece of DA revo shooting. I'm also persuaded that it's a relatively individual affair; but what works for one person will probably work for at least some others, so I'll share my thoughts.
For the first couple of years of revolver shooting, I listened almost exclusively to the advice of the old classic revolver legends: Bill Jordan, Elmer Keith, Ed McGivern. Only recently was I persuaded by a local IDPA Master (a level to which I aspire, hopefully this Spring or so) to try a grip that is much more in line with the popular iscosceles, high-hold grip clearly based on the competitive dominance of the 1911. I tried it and immediately shot my best three consecutive matches ever.
The grip is basically a thumb-up on the strong hand, as if it were riding the safety of a 1911--but instead, my thumb just goes up over the grip hump and rides lightly atop the cylinder release, parallel to the hammer. My hold is closer than before to in-line with the bore/recoil axis; my sights track straight up and down on the recoil impulse; the slight and unavoidable flexing of my thumb (involuntary companion to the trigger finger's action) does not push the gun sideways and out of alignment; and my index upon pushing the gun out is remarkably consistent compared to my prior experience. The only down-side I've found is that the joint of my thumb gets sore. I'm hoping this will fade. This grip works comfortably with everything (for me) up to standard power 45 ball out of a 625, or 38+p out of my 340PD. Not so good for full-power big-bore mag loads.
My off hand does not ride the frame under the cylinder, as my friend suggested; but it does achieve a better contact with the gun's grip, and is unimpeded by the thumb of the strong hand, which is now out of the way.
I haven't read the article you mention about Miculek's grip, but you can bet your bottom dollar I will; because the grip is essential to revolver shooting, and so little, relatively speaking, is written about revolver shooting at a competitive level.
As far as your concern about what's appropriate for a defense situation, I honestly don't see how something that makes my shots faster and more accurate is not a good idea. I mean, if I get a faster draw and a faster and more certain first shot, that means I'm getting a consistent grip, right? I know one-handed practice is important, and I'm willing to put it in; but if I CAN use both hands in a defense situation, you better bet I will, because I know I'm faster and more accurate that way.
Okay, sorry for the dissertation, but there's not near enough said about these matters, if you ask me, so I'm just trying to do my part.