Personally I didn't mind the introduction of Mark, nor did I think it was handled sloppily. I actually enjoyed having this new character thrown into the mix right from the go and slowly trying to figure out his back-story through dialogue and watching his interactions with the other characters.
He also played a big part in painting a picture of the past three months and how all the other survivors were getting along during his talks with Lee. I think he worked really well as a character and a plot device.
It's too bad he had to go in such a horrific way, but that's how it is in TWD.
I thought he, Clem and Carley were the most likeable/dependable characters in episode 2.