I really like the blend of 2D and 3D components in the game. I actually found the game pretty easy, usually I would kill an entire group of enemies and have to wait several seconds for the next group to move onto the board. Eventually I ran out of space and started stacking Boarbarians at the end of the path just in case, but I never needed them. I think for jam games it's always better to err on the side of being too easy :-)
I think thematically it would make a lot of sense if you could upgrade your heroes stats/gear, and that might open up some more interesting gameplay decisions as well.