Yeah, Halo was really good for balance, too. If you sucked with the sword but knew you could area-blast with the bazooka, you knew where to go and how to fight if you wanted the best chance to win or level the playing field. If you couldn't aim for shit with the AR, you knew that you needed to lob grenades and try to get to a shotgun.
COD answered that with perks and by making sure that the "best" guns were available relatively early. You could kind of level the playing field by masking your weaknesses with intelligent loadouts. A really good player is deadly with an AK47, which isn't unlocked until way late, but a decent player has a fair fight if they use a P90, which is available early, and has certain perks selected to go with it.
Different ways of allowing players to mask their weaknesses, but with pretty good results in terms of online play.
Now, with micro-transactions, you can just spend money to hide your flaws. I won't do that lol.