Certain Affinity may initially give off the impression of being a Diablo or a Torchlight, but the game is far more focused on keeping the action going than fiddling with RPG elements and menus.
The title supports up to four players in every combination of couch and online co-op. However, there are only three classes, so a four player game will have two folks playing as either the mercenary, wizard or assassin. Actually, all four players can rock the same class if they'd like, but it's definitely better to have diversity of expertise on the field.
There is no skill tree or leveling in Crimson Alliance. Players acquire gear that increases their armor, which increases their health. "Leveling up" is all based on gear gathered from the "crafted" (i.e. pre-generated) dungeons and loot drops. It's also possible to purchase items in the store, but I didn't get to see that functionality in the demo.