The game is relatively unbalanced. Depending on the playstyle of the characters, the game gives some characters an unexpected unfair advantage. For instance, Superman, a strength buff, has most of his prowess using heat vision from across the screen. Deathstroke has a mean lame game, however, he has a ridiculous amount of mix-ups up close. His set-ups for when you are getting up are sporadic and unpredictable if you haven't already telegraphed his moves. Smart Doomsday players know when to poke you, and the super armor for that character is almost impossible to deal with. The fact that every character has pretty much the same speed of dash- and length, makes running away and getting close to characters with range advantage incredibly difficult. The biggest fault of this game IMO if the lack of ability to air block.
Many people complain about my main, Aquaman, being broken because of his "slippery" hero trait. There is an easy way to deal with this- lame, juggling, and grabs. Although it's a pretty good trait, it doesn't stop a mix-up from happening into an juggling combo, or a grab combo like Grundy has. What makes Aquaman extremely good in this game- is he can convert off of most of his attacks. For his set-ups he has a low, med, and high conversions that can lead to a minimum of 32% with no MB. His medium-close range trident let's him poke enemies from a safe distance, and he can do it fast too. With unsuspecting projectile moves, he is really broken. If he isn't already being zoned.
The game is broken when you consider lame, but when the fight gets up close it's a bit balanced, albeit Deathstroke and Aquaman are really good up close.