Wall - one point wonder, or worth investing?

[tofucsek]

I've never been a "wall using person" myself.
However 5000HP and +30 defense upgrade can be tempting (fully upgraded), also the fairly low rage cost and high XP that it gives.
Probably there are people who could answer your question more accurately, my experience is on lvl 20ish, wall only upgraded once or twice, the enemy comes through of it like it wasn't even there. And the enemy units tend to destroy it if the stack is capable of doing it with one hit so AI doesn't even bother go around it anymore.
Maybe if you are a mage and you want to lvl up your dragon I can see this as an option but at the end game... maybe not the best choice.