Ash,
If I understand your question correctly, there would have to be some language added to the rule that would count the dealer as one of the persons when considering "substantial action."
In your example: "the second last player is skipped" leaving only one remaining player (not enough for "substantial action"), the current rule would create a situation where it is necessary to "replace" the proper board card...in fact, if the round were checked, it would require more than two actions so "substantial action" would be impossible.
This example is one of the reasons why I lobby for different rules for head to head. How is substantial action even in the vocabulary? Impossible!
Here's the way I would rule: In the event of a skipped player followed by one calling player and a "burn and turn" from the dealer...the skipped player's hand is dead. The skipped player should have enough time to realize that the player to his left acted out of turn, and the time it takes for the dealer to "tap and burn" should have given enough time for the skipped player to stop the action and draw attention to the error before the board card is prematurely turned.
The only time the "proper" board card should be replaced is if the last player were skipped and the dealer burns and turns before he acts.