I played the game for a month or so
Interesting concept - the classless system is a neat idea, plus the whole "arkfall" thing is kinda neat too - but it lacks something that WoW was reasonably good at incorporating later on: You effect on the game world.
It seems like no matter how often you wipe out hundreds of identical looking color-coded hellbugs, or bandits, or crazy cyborg miners, or emo alien deathsquads, then you never make any meaningly impact on the game world.
WoW at least got that somewhat right via instanced game-world content that changed as you did various quests.
Plus, while Defiance gear is balanced in such a way that an epic tier rifle isn't that much more powerful than a beginner tier rifle - then it just has a few more slots for 'synergy' bonuses, is a nice idea to make sure that high lvl players aren't that much more powerful than low lvl players... well... it also means that having played the game for a month and leveled your character up quite a lot feels like very little actual progression.
Heck, considering that PvP is neatly hidden away and in no way allowed in the main game world I don't see that much of a need for weapon balancing in the main game. Sure, it means that the devs don't have to do much for pvp balancing either, but it makes for a somewhat more boring PvE experience.