Game design goes through a lot of iteration to find the most engaging combination of mechanics within the scope of our goals. We naturally try a lot of prototype variations even with a strong starting idea.
We tried a few alternate mobility abilities for Overrun. One of the first ideas was a short range dash that would toss enemies into the air behind him if you impacted them. It was fun to use but the transition from third person to first person and trying to turn around to shoot them wasn't easy, and solutions like automatically doing a 180 with the camera took away control from players.
The weapons had a couple alternates such as a flamethrower or incendiary grenade launchers. There were a few attempts at having two very different firing weapons in each hand, so one being hitscan like it is now and the other being a travel time projectile. It didn't play as well when trying to fire both at the same time unfortunately, especially in versions where they have different firing rates and how you want to aim travel time projectiles by leading a target, and tracking the ammo pools separately is difficult.
The Cage Fight ultimate was pretty successful from the start, but we still tried other versions to see what would play best. It was a physical wall instead of a barrier at one point. There was also a completely different ult that was more of an area effect debuff to enemy damage dealt, the opposite of damage boost.