Well if you havent found iron I guess you should just go straight and dont care about anything. when you hit iron the clear up the stones and stuff, which is the most efficient I think since cave-in only happens outwards rather then inwards.
And yes its more like a gimped minesweeper game since we cant choose another tile if we found a dust tile. At least now its somewhat predictable now.
I havent mined alot but it does seems like unstable node do stack with each other. You can find a spot with lots of cavein node, then a spot with nothing for a few tiles wide.
The only reasonable suggestion I can give is, when you hit dust, go left or right, if there is still dust go back one step and go left left up, or right right up. All of this while checking for dust of course.

green circle = no dust, yellow = dust, green square = confirm no cave in.