The phrase "new subclasses" refers to new categories or types that are created within a larger group. It means dividing a main group into smaller, more specific groups. Full definition
To battle back the Darkness and the Taken army, players will get brand new subclasses with new supers. (gamerassaultweekly.com)
Titans, Hunters, and Warlocks will have new subclasses with powerful abilities to master. (blog.us.playstation.com)
New Destiny expansion details have been leaked, including the official name and the price, new subclass details, new super abilites, new maps, and a new raid. (mmogames.com)