They're not running through, they're trying to pass without attacking it. So HP is irrelevant here.

Hello guys

I'm very new to this game (I don't even have bought the full game yet).
I tried this (http://i.imgur.com/EyWBS2p.png?2) in the lvl3 of the beginner campaign.

The ennemies don't even try to kill the furnaces and sometimes get stucked behind them.
Is it intended ? Can this work in the ...