I disagree, I don't think it's well balanced at all and some character functions leave me scratching my head.
The thing is, characters throughout KOF usually gained moves on top of retaining many of their trademark moves. Ryo is one of my favorite examples of this, just compare him from 94 to XI, he was no doubt at his peak in XI. Now he's back to being a pretty boring and vanilla Ryo, he's lost a ton of stuff that made him versatile. Then there's Ralf and Clark, those two grew alot throughout the KOF series. Looking at the duo in XIII, they've lost alot of what made them so versatile as well. I think Ralf lacking the SAB hurts him alot, while Clark lost alot of moves that made him a real threat.
Occasionally a character would do a complete 360 like Kensou and Robert in 1999/2000, or Takuma in 2002, but some of the changes and/or reversions made in XIII seem to be for the worse. In 1996 SNK wanted to lessen the effect of zoning in KOF by giving many characters short range projectiles, and while this had some mixed results, I think Andy was one of the best to benefit from this change as he gained new moves to compliment it, he went from being a SNK shoto to pure rushdown style with high/low mix-ups, plus a proximity unblockable. Now he's basically in the same boat as Ryo.
Takuma I think is a pretty decent attempt on taking a new spin on an old favorite, and although the things he is capable of now is utterly ridiculous, I like where they went with him, although I do miss the Moko Buraigan. But it's obvious they had to cut corners on him, I mean c'mon... Kyokugen Kou'ou Ken? The lack of his overhead command normal is disheartening too.
I think the character that has it the worst though is Maxima. His entire special move list is some variation of the Vapor Canon. He lost a ton of stuff. It's like all he has to compensate for it is large amounts of guard points, but even then, his normals have never been slower and his moveset anymore lacking.
Then there's characters like Duo Lon... I remember Duo Lon being a real piece of work in his debut in 2003 and in XI, but I feel like he was just cut in half. Then there's Chin... I feel like Chin is just a really gimmicky character now, he lost alot of what made him unique.
I just think for the next KOF title, it needs to be fleshed out more. XIII just leaves me feeling like it's still pretty barebones for a KOF game, and I'm not fond of the game revolving around loops like if it was some kind of anime/marvel game.