Considering it's pretty damn obvious you don't really like Nightwolf, let's get something straight here. It was clear, by story mode standarts, that Nightwolf was most definitely not a "random shmuck", he was the second in command after Raiden. He defeated Quan Chi, killed Noob Saibot (apparently) and saved Earthrealm souls all by himself. It was also in his command that Lin Kuei failed. When Sindel approached the heroes, it was pretty much stated for us viewers he was clearly the only one capable of defeating her there. This was not a "random" twist in the story at all. If you don't like a character and think they're "shmuck" fine, but LOL saying Nightwolf biggest contribution was being defeated by Scorpion (licking his balls already?) proves exactly that your point is flawed and it's mostly subjective of course. You are ignoring what you don't care because he's a character that you don't like no matter how important those scenes were for the flow of the story.
At least have the decency of weighting all facts that the story mode presented.
That being said, Sindel's scene was indeed over the top and she could have very well only killed Kitana.