Man, it looks like you are outsourcing the most fun part of your game? I have my own project to work on, and have little know how on UE, but I am open to a discussion (don't need money) to help you lay out the right system. You need to start with some other questions first though. For instance: fighting games tend to be tuned around the baseline fastest attack (see Tekken 8frame punch), but this is a "fair" PvP game. The principle stays though: what should be the fastest attack and at whose disposal should it remain? When do you want the player to be hit? What about concurring attacks? It all starts with the design philosophy. The combat itself can be satisfying on 2 levels:
- learning and pattern recognition (letting the player learn the rhythm of the game, extend and interpolate the patterns);
-visual and audio feedback ("juicy" animations);
Mind you there are aspects that tie these together, so for instance if your background or music play a certain frequency, then the pattern recognition extends to those media.