Why Auto-Battle is Worthless

[Skyblade]

The auto-battle system, despite what the game may tell you, is not designed to create efficient battles. It is designed to make battles prettier. Don't believe me? Go test it out. Playing as a Ravager, I've noticed the game make inexcusable combat choices just to add variety. My Magic stat is a hundred points higher than my Strength stat, and the enemy has a single weakness, to fire, and no extra mitigation to magic or physical damage. So what does auto-battle do? Fire, Flamestrike, Fire, Flamestrike, Fire. Why? That's not the most efficient use of my abilities, because Fire does way more damage, and they both chain the same amount. Or, even better, after I stagger the enemy (despite staggering adding no elemental weaknesses, I checked), it starts tossing Watera and Aero into the chain. Just to make the fights look prettier.

The only time the game seems willing to chain the same command together (for an attacker) is the Commando's Attack command, and that's only because the attack animation changes depending on where in the chain the command is.

Then too, the auto-battle is incredibly terrible at noting stacking bonuses. Against an enemy with neutral elemental coverage, but who resists physical attacks, it spams various different elemental spells. If an enemy has an elemental weakness, it will use that element. If you combine a couple of those things, will it use only single element spells? Nope. It's never stupid enough to use things the enemy is immune to or absorbs, but it is perfectly happy to put out half a chain of 1/10th damage Waterstrikes. You can put Faith on to stick to just spells, as long as your Synergist isn't AI controlled and just going to put Bravery on as well, which will cancel it out for weakness calculations, no matter which is stronger.

Not to mention the abysmal intelligence of the part of battle you can't control, character positioning. I'm fighting enemies with AOE attacks, and I'm using spells with infinite range. Why do my characters thus constantly try to group up on the Sentinel?

[ShinGundam]

Fire, Flamestrike, Fire, Flamestrike, Fire. Why?

Flamestrike is Alternating physical and magic builds the chain gauge faster.

it starts tossing Watera and Aero into the chain. Just to make the fights look prettier.

ra spells do bonus damage to staggered enemies (Fira / Watera / ETC; they do about as much as two fires, then bonus if the mob's staggered) and Aero it's the games way of increasing the chances of juggling them succesfully. Also, If an enemy is resistant to spells, it will puts in the elemental physicals only. If and enemy is resistant to physicals it puts in spells only (usually).

[Skyblade]

I hadn't noticed alternating physical with magical increases chaining any, but I'll experiment with it.

The reason it uses Watera on an enemy weak to Fire instead of Fira is..?

And Aero should then only be added if the enemy is Launched, or is at least susceptible to Aero's stun. And this is not always the case.

[ShinGundam]

The reason it uses Watera on an enemy weak to Fire instead of Fira is..?

I don't know, i have played it in Japanese last year, but here is a FAQ for game mechanics might help.
GameFAQs: Final Fantasy XIII (PS3) Game Mechanics Guide by ximaus