The premise is very cool. I can imagine a movie scene with two characters back to back fighting off a horde of enemies. That evokes a really fun fantasy. I also like the mechanical concept of controlling multiple avatars. The RTS genre gets a lot of its cool factor from that, at a much larger scale.
I had difficulty controlling the characters. I found my brain twisting into a metaphorical pretzel trying to switch between something even as simple as two adjacent rows of keys and which mouse button to press. An extreme comparison would be like trying to play with two separate controllers. Chaotic, at least for a game of this speed. I wonder if something like a button to toggle between the characters would work better (for me). I would be able to keep my fingers on the same keys for moving left and right. Having the "switch character" button be convenient would also be a consideration. Spacebar or right click jump out at me.
I like the simplicity of it too. Scope creep and bloated ideas are especially bad for a short jam. I tried to be better this time around, with mixed success. Arcade style games seem to be a good approach. Short, simple, elegant, quick to pick up and play.
Congratulations on completing what you were able to. 72 hours always turns out to be such a short period of time. Keep up the good work!