There are many characters faster than Mileena. She is weak in many ways, but also extremely effective. I don't view her as cheap, though what you say does apply in many situations. She is fairly well rounded and can do almost anything decently... She excels at punishing you for practically anything you do.... That makes defending against a well played Mileena very difficult. However, you are only on one side of that equation. The Mileena player who can dominate like that puts much effort into making her effective, unless they've found some secret way to avoid all of Mileena's flaws.

I use Sektor, he was my main in UMK3 and is my main once again. His flame thrower's reach and block stun are a thing of beauty. He has a lot of tools to deal with the turtles, although Mileena's and Skarlet's projectiles are the best since they're faster.