Obviously this post hinges on the uneasy idea that Guardian is XP-related progression, there will be some level of progression, "•Create your character, [u]forge[/u] your legend by defeating powerful foes, and earn unique and customizable weapons, gear, and vehicles." (via GameStop Destiny page). Halo: Reach's progression system, imo, was awful. If Destiny ends up being a title with a XP-related progression system like Reach's ranking system, then Bungie needs to do a lot of proper balancing between enemies. I'll try to create an example from the info we know, if on Mars there are only Cabal and on Venus there are only Fallen and say for each kill of the Fallen if 15 xp and for each kill of the Cabal is 17 xp, then based off the visuals of the characters alone I would probably want to start farming Fallen for XP because they are (this is an assumption) the weaker enemy between the Fallen and the heavily armored Cabal. Consequently, I would only go to Venus and shun the rest of the game, drastically reducing the meaning+purpose of the game. There are a lot of us gamers who are obsessed with the progression of our character and will find any exploit we can find in the game (i.e. all-grunts + fuelrod cannon in Firefight = easy xp) to get ahead. The weighting of enemies and the xp they grant has to be carefully tuned, and there [u]must[/u] be easy settings for you guys (Bungie) to tweak this game without requiring a title update, tweaks to weapon balancing, xp earned for "Faction Wars" and defeating enemies like Cabal or Fallen, and general settings and features that we, the gamers, may not know yet. If anything, Bungie, revolutionize the progression system in ways that we (the gamers) couldn't have imagined, and set a precedent. tl;dr If our guardians level up through earning xp, avoid having enemies that are poorly weighted in terms of what they give for xp. Us gamers see exploits to leveling up our characters in many games, and we often take advantage of them. Destiny should have tools for Bungie to make easy tweaks and updates to the game without actually requiring an official Title Update, and many of the tweaks should be a product of community feedback. Hopefully Bungie will even look to move on from XP-based progression systems and set their own ranking system precedent in the industry.