But Dissidia's dash-around combat system would allow for multiple adversaries.
The mechanics of Dissidia are based on a polar coordinate system with the enemy as the origin. Which basically means everything you do is based on the enemy.

In a game like Super Smash Bros. it is based on a Cartesian co-ordinate system where everything is based off of the background, something which is static for all players. So not having a focal enemy can make sense. However the dissidia gameplay is essentially designed around having one enemy as the entire focal point for the game design.