DC Universe Online has an unusual combat system for an MMORPG. Instead of a system like World of Warcraft where each action requires mana, is performed by using a command and requires time to recharge, in DC Universe Online each action or technique corresponds to a specific button and is immediately performed in real-time each time that button is pressed, without cooldowns or mana requirements to worry about. Along with interactive environments and a fully-fleshed physics engine, the combat in DC Universe Online is more akin to an action game than a RPG.Ars Technica: Intimate and Interactive with SOE and DC Universe Online (January 8, 2009)

DC Universe Online doesn't have classes. In World of Warcraft you choose between a Warrior, Mage, Priest, Paladin and the like, but in DC Universe Online, building your character is simply a matter of choosing specific powers to tailor to your play-style. You can build a healer character or a tank-type character, but they will never be designated a certain role. The stance system also creates a lot of flexibility - any character can use a certain stance that will enhance their ability to take damage, do damage or heal and support. Though a damage-type character in heal stance won't ever do as much healing as a true healer character, the system still allows for greater flexibility when playing in parties.