When most creatures get vigilance (or defender or reach) they move to the bottom of your creatures, so they attack first, and are the first attacked. Veteran warleader doesn’t do this. That means your other creatures can be picked off by aggressive creatures, and attack into defenders before warleader can clear them out.
Why doesn’t it move? That seems weird.
Can you list the creature names or situations in which vigilance was applied to help sort out an answer?
I mentioned Veteran Warleader in my OP. I don’t know if any other creatures get a temporary vigilance bonus.
From what I understand, vigilance in this game is like a soft defender. The creature with it will only defend if nobody else has defender or reach and that’s why it stays in 2nd or 3rd creature position.