The simple fact that you're still unlocking stuff until SR130 means that there's going to be at least some imbalance. Not everybody plays all that often, and when you only have time for a couple of hours a day and you can only play once a week, it can take a good long while after you get the game just to finish the "primary" ranks and unlock everything besides what the specializations grant. By my calculations, assuming no double XP codes (which haven't existed since early 2013), it takes about 75 matches just to reach SR26, which is when you've unlocked all weapons and AAs (but not all perks). At 8 minutes per match (a conservative estimate), those 75 matches amount to over 10 hours of play time, not counting time spent in lobbies waiting for matches. To get to SR50, it takes about 4.7 times as much XP as it does to get to SR26, which translates to almost two whole days of play time, and it takes over four times as long as that to get to SR130. In addition, there's always going to be new players dumped into the game at SR1 having to fight against players who are all maxed out. So, while most of the important stuff is unlocked quicker than in, say, COD or Battlefield, it can still take a while, and it can take even longer to unlock everything, and in that while the fact that you can still get matched with people that have everything is inherently unbalanced.

Another problem is that even if you have a bunch of SR130's fighting each other, it's still hard to make sure everything is balanced. It's an inordinately complex systems with way too many variables. It used to be everyone started with the same gun and grenades and identical attributes. A perfectly level playing field is easiest to balance. With Reach's system, it's a bit more complex, as you have to make sure that no one armor ability is no stronger than the others. But in Halo 4, people can spawn with whatever weapon (primary and secondary), grenade type, armor ability, tactical package (perk #1), and support upgrade (perk #2) you want. The amount of variables there is staggering compared to even Reach, and it's impossible to make sure that there's no one loadout that's more powerful than another. Add in the fact that not everyone in a match is likely to have unlocked everything, and you can see how unbalanced everything is.

This is exactly the case with COD since COD4, and it's one of the reasons that series cannot hold my interest. It's a complex and unbalanced mess. Balance was sacrificed in the name of greater customization. But that's what COD does, and people like COD for it. COD wasn't popular until it introduced all that Skinner box crap. 343I thought they could emulate that success in Halo 4, and it failed miserably. Halo was already popular before Skinner boxes became the norm. Having a level playing field is what kept Halo 3 unique, and even Reach still technically had a level playing field as loadouts were simple, always preset, and usually only varied in terms of which AA they offered. Bungie never made us jump through hoops to unlock things that affected gameplay in Halo, and they kept it simple. Having a simple, perfectly level playing field is what defined Halo before Halo 4, and it should continue to define it in the future. Combat should evolve in other ways.