I wonder if placing humans down for defense is unintended considering how finicky it is. Besides the weirdness with placing them, if they fall in combat you can recollect them just like if they were defeated as enemies. While they're fallen down though, they still count towards the total defense points. So if you don't collect them quickly, you can't deploy more defenders.
That aside though, I pretty much feel like I need to use humans now due to the addition of the crossbow goblins... The crossbow goblins are sooo bad considering the deployment cost and they reduce the amount of the other goblins you get haha. The game is so much harder now than it was in the previous version.