"So...what am I supposed to be doing?"
More than any other thought, this was the phrase that echoed through my mind during just about every moment of Defiance when I wasn't actively pursuing a quest. It's an MMO, but it doesn't include most of the tropes we've come to expect from the genre. Namely: a goal. In place of traditional elements like social interaction and leveling, we get a shooter sandbox that is extremely laissez faire about what you do with your time. Whether that's a good thing or not depends on what kind of player you are.
As a huge fan of exploring digital worlds in MMOs, I spent much of my time cruising around the fairly small world of Defiance exploring what the game world had to offer. However, the game world is fairly bland so I'd jump into a few throwaway quests about rescuing five medics or activating a radio tower, but throughout the game I felt a complete absence of a guiding hand. There is no indication of what the point of Defiance is. Maybe that's it though. Maybe Defiance is just an open world play set. It's a ball of clay that players can use as they wish, but with all the inherent limitations of simple, unformed clay.
Trion has been talking a big game when it comes to Defiance. Their company line is that it would be a groundbreaking cross-medium world that would link Defiance the television show and Defiance the online world in exciting ways. However, the reality is nothing quite so grandiose. Basically, Defiance will include episodic story-based missions that give a nod to the events of the show.
From what we've seen of the story the game currently offers, we're not entirely optimistic about where these missions will go. The game's characters only show up rarely, but are unlikable and devoid of any personality beyond the snarky guy, the serious guy, and the smarmy guy. Meanwhile the paper-thin storyline doesn't involve the player in any way more significant than making you someone's lackey for a short while. The result left me feeling like the odd man out--the way a courtroom security guard must feel. There are stories here, but it's tough to care when you're just the muscle. I'm sure this alien technology you discovered is fascinating, but you don't pay me to care about the details. Just tell me who to shoot.
While Defiance fails at story and characterization, it picks up the slack with its solid core gameplay that is reminiscent of a third-person Borderlands by way of Trion's previous (highly underappreciated) MMO, Rift: Planes of Telara.
Unlike other MMO shooters, such as Tabula Rasa and Global Agenda, all the action here is in real-time. There are no skills to exhaust, no global cooldowns, and no automatic hits. This is third person shooting like you'd find it in any action game, and for the most part it feels pretty good in the moment-to-moment battles.
It's buoyed largely by a fun Borderlands-esque system that ensures you're constantly getting unique weapons like electric shotguns or sub-machine guns that shoot flaming bullets. The breadth of possibilities isn't nearly as vast as Borderlands, but there's an irresistible pull that comes from getting a cool new weapon. You must go try it out.
The real trouble with Defiance is that the core gameplay is all it has. The progression that you'd expect to find in an MMO (level up to tackle more difficult dungeons and cooler content) and the story you'd expect from a shooter are gone in Defiance.
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It straddles the line between an MMO and an open world sandbox game. It's an online-only world with hundreds of other players running about, but there's next to zero social interaction. In the entire time I played Defiance in preparation for this review I never once spoke with another player, which gives the game a lonely, crowded feeling like a nightclub where everyone is dancing alone.
The one moment when the isolation breaks is during the Arkfall events which are essentially the same thing as rifts in Rift: Planes of Telara. In these events, a giant piece of alien technology or a boss monster emerges in the world and dozens of players swarm the site, whacking it like a giant pinata until it spews loot.
These moments are fun, but can become a problem when swarmed by dozens of other players. The enemies in an Arkfall seem to scale in difficulty according to how many players are present. So if there are too many people there then your bullets might as well be ping pong balls.
Apart from the episodic story missions the only lasting allure is PvP. While PvP is occasionally fun, it won't hold most people's interest for very long as the main modes feature only two maps, and there are some glaring balance concerns.
Defiance's faults are a lot more forgivable though because you're not being asked to pay a subscription fee, and there's nothing else like it on consoles right now. The novelty alone might be worth it for some players, but Defiance struggles in the long term. Without a story or sense of progression it is all too easy to imagine Defiance collecting dust after a few play sessions. 
This Defiance review is based on a digital PC version of the game provided by the publisher. The game is also available for PlayStation 3 and Xbox 360.