Snow's a freaking tank. He's perfect as a Sentinel. I actually prefer him least as a Ravager because, even at Chapter 11, he only has ice and water spells, like he has some affinity to them cause of having Shiva as his summon. But that rule of logic doesn't apply to Lightning. She's a pretty awesome Ravager actually. But if you want a Commando, then Fang should be the de facto choice. A friend of mine said it best, she' s like Auron on steroids
I don't know if this is an indication of how you will find the upcoming battle, but I beat Dysler on my 2nd go, and without too much hassle, but I really struggled against this one. More so than any other boss in the game, more so since Seymour in FFX

I switch my party leaders quite frequently, if only for a change. Mainly it's playing as Lightning cause, you know, she's badass. And I prefer to let the computer be in control of characters like Sach, so they can handle the buff/debuff abilites for me.
This is gonna sound really weird, so bare with me. But the one thing I like doing, and always tend to do, is that when I'm about to open a treasure chest, I rotate the camera angle 180 degrees so I can see the character's face when doing it. Cause most characters, especially Lightning, look completely uninterested

But it is true! You can wander around as someone in the field and they appear fine, approach a chest and their mood just darkens. Even Vanille!