My iron shots have never been great but recently I tried closing my stance (lead foot forward 3" slightly flared out) but keeping shoulders square. In addition I also closed the face but only very slightly. The result was excellent, sweet spot strikes with 8 or 10 consecutive straight shots on the range. Whether or not this is a compensation for a slight out to in swing, I don't know (and don't care!).
To gauge the amount of face closure, I put myself into impact position with the face square, ie weight on lead foot, hips opening, shaft forward but then simply return to address, the face naturally closes slightly... leave it like that and swing. The face is then square at impact.
The main reason I closed my stance was to try to eliminate the shank when using wedges or even up to a 7 or 8. Like many other golfers, my shank was due to my right knee and hip moving toward the ball. I find now if I set up everything all square then pull back my trail foot by 2" or 3", my shots are solid, straight, and the shank has gone. The fear of standing on a par 3 or a short wedge in on a par 5, knowing a shank is imminent has disappeared.
This works simply because I've given my trail hip further to travel toward the ball and the hosel never gets as far as the ball.
I've had lessons on the shank but no-one has suggested just pulling back the trail foot. Try it, it works!