Hey really awesome idea! I love the idea of trying to lead an entire army to try and stop the "Good" hero. The back story is great too, he just sees them all as money bags!
Overall I liked it, though it started getting super laggy for me, like feeling 10fps or so. Once some guys died it helped. Also I had a very close battle where I had one guy left and it looked like we knocked out the heroes health all the way down, but then he got us and he kept going. Maybe he still had like 1hp left... but the goblin tribes were doomed.
Overall really cool! Slightly similar in concept to my game where you also fight heroes and have minions to help, but yours is much more focused on the minion/army/economy aspect (mine leans towards survivor like). Anyways very well done! Very awesome game you made!!