I only use 3 classes for BOPS II. An assault rifle class as my bread and butter class. A semi-auto assault class for hardcore. The third is a sniper class just for the times when you're hopelessly spawn trapped.
For Halo 4 I use four classes. 2 classes for BTB, 1 for maps with a lot of vehicles, 1 for maps without. A class for more close quarters maps like team slayer or regicide. And a final class for 1v1 clan compete matches.