Really cool concept. The pulse attack makes you consider the other player's positioning when lining up your shot, which feels like a relatively unexplored and exciting design space to me. The closest analogy I can think of is support characters in League of Legends. Often they'll have to line up their abilities based on their allies' positioning, rather than the enemies.
The tether is fun to watch but unwieldy. I think a straight line between the two characters would have been more reliable, easier to program, but still just as innovative. I'm sure you had many other ideas for abilities based on tether physics, but I think another cool area for exploration is enhancing movement instead of combat (e.g. Knuckles Chaotix, Ice Climbers Up Special in Smash Bros), and another random thought I had is the idea of timing a button press to return a pulse from your ally (e.g. Mario Tennis, Legend of Zelda: Wind Waker Phantom Ganon boss battle) for more power or something, etc.
Love the character designs. They each have their own charm and they complement each other.