You don't need any of the GoW2 DLC's to get a Level 100, but if you are trying to get the achievement for earning your Level 100 achievement than you have to have the Snowblind DLC.
Originally Posted by IBYCFOTA
Gears took the core mechanics of what made the multiplayer special and either removed them or mangled them beyond recognition. All this for what? To attract the gamer with the attention span of a nat who will play the game for a month and then go back to his favorite FPS or the next flavor of the month title? They're not the ones who are going to be buying all of the DLC and still playing the game 9 months after launch. That would be your hardcore fanbase, the one you've alienated with your changes to the point of no return. Remember them? Don't worry, you will soon enough.