Did i make an oopsie ?

Hey, this is my first playthrough and i'm afraid i might have messed up.

So there is this Mutasafen guy you encounter for the first time in act IV, when you reach the middle-city. The fight is scripted as he's supposed to teleport away when you bring him below a certain health threshold.

The thing is i had him stunned, staggered and prone. His "That was educationnal. I must take my leave." line triggered but he couldn't do jack shit. And then i finished him off.

It didn't feel right at all so i looked it up a bit. He's supposed to have an entire questline in act V. Did i miss out on something important ?