1. Yes, there is a stat that affects spell casting. It's neither DEX nor QUI, it's Agi. Both DEX and QUI add Agi, but QUI adds a tiny bit more Agi than DEX. (DEX adds 1.6, QUI adds 2.0). Taken from Jwiki, a Magician with 18 Agi, will cast Grade 1 Banish Blow I at about 12 seconds. However, one with 26 Agi, casts Grade 1 Banish Blow I at about 11 seconds. This is with Qui, and not DEX. So, DEX is proven NOT to be the only stat that effects spell casting.
As for stat builds, both of them, I don't like. Both of those builds give you TERRIBLE HP. If you get ambushed, your character WILL die.
I suggest a build with Vit, so you won't be completely annilated by spells or ambushes. I did VIT/QUI/MND in CB, and it worked fine.
2. Ranged attacks can NEVER be countered. (Just think about it, how2counter arrow.) Magic will never miss, and can never be countered. However, it can never critical :x.
3. Yes, a magic using pet would probably be wise (or a Ranged pet). Really, it could be anything, but magic is probably the best to use, due to how powerful it can be.
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