If you haven't played this game: please read this!
Today I had an epiphany and realised something so fundamental to the combat of this game - well it was a mixture of an en epiphany and the game vaguely mentioning it enough times that made me realise.
The key to combat in XC2 is blade combos, more specifically constantly chaining blade combos so that you can unleash a level 1, level 2 and level 3 combo, then rinse and repeat. This will reduce battle time from 10-20 minutes+ against a regular frog or rabbit to a matter of one minute or less. It's so fundamental to the game but the game doesn't explain it.
Basically, auto-attacks are almost irrelevant (I guess that's the reason they're automated). Arts do a little damage and have other important effects like breaking, toppling etc (the game eventually does expain this well). But if you just use auto-attacks and arts with the occasional blade combo when the prompt flashes up on the screen, without paying attention to chaining blade combos together, battles will take an awful long time.
What I mean is, the move that you can activate by pressing A for your main character, or ZL and ZR for the other members in your party. At the start, this will always be a level one move (for a lightning blade, Volt, for a a fire blade, Burn, etc). You then have a period of time, indicated by a bar on the top of the screen that slowly moves down, to chain the next move, which will be a level 2 combo (for example, if you start with a leve 1 earth combo, the level 2 fire combo is Volcano). And then you have a period time to activate the level 3 combo in the chain, which will do massive damage.
The thing is, elements always chain into the same elements. Earth - Fire - Earth for example. Any one element can be chained into only two elements at a particular stage (this information is visible on the top right of the screen where you see the whole possible chain in coloured icons from beginning to end, so for example if you start with a fire move, it will show the two available level 2 blade combos that can be activated, and the two level 3 blade combos that can be activated for each of those).
With this in mind, the most important thing to consider is the elements of the blades in your party (since chaining is defined by elements). You need to have elements that you can chain to use a level 3 blade combo. It's no good using a level 1 blade combo if no party member has the appropriate element for a level 2 combo. Even only getting to the level 2 combo is useless, you need to activate the level 3 combo.
An element can always chain into the same element ( e.g. Fire-Fire-Fire) so having two characters with the same elemental Blade is one good strategy, however one character is usually not able to activate the entire chain by themselves as they will not be able to activate the next move in time before the timer runs out.
However doing things like breaking and toppling the enemy will increase the timer and allow the same character to keep the chain going.
But just with the standard elemental type of your starter blades it's easy to achieve level 3 combos over and over again, once you know what you're doing.
What I've written might sound complicated but if you play the game you'll understand what I mean pretty quickly. There's no doubt about it, this is how you are supposed to fight enemies in the game, it's what the designers intend you to do.
If you don't do this, combat will make zero sense. If you do, it becomes a lot of fun.