(I've read all the short stories, haven't dipped into the novels though.) For anybody else who's curious, you want to focus on the first three skills in fast attack, the last two in strong, everything in dodge, the first two in aard, maybe the first skill of axii, the second skill in quen, and mutation skills if you want synergy.
Geralt does use axii to manipulate people, but not often at all. Igni is op, book quen is a bubble like the alt skill, and yrden is nothing like in the book. I guess yrden's a kind of seal, or ward, but its contextual. Only seems to be useful repelling basic curses and spells. I want to say there's another sign, but I forget which story its in. Somewhere in The Last Wish, maybe.
Also, there aren't really any decoctions, but the idea behind them is basically there. Potions activate Geralt's mutations and cause him great pain - think the W1 intro vid against Foltest's striga. They may unlock abilities dormant in his mutations, but they definitely aren't just buffs. That's why normal people die drinking one - they're just deadly intoxicants, on their own. Use potions very sparingly.
Geralt does lose fights. He's a great swordsman, he can even deflect arrows, but several skilled opponents could kick his arse to next Wednesday. In fact, he's just as often bested, captured, or severely wounded as he is victorious. Get mobbed, and Geralt's sure to die, so there's no shame in running. He prefers running to dying.
A combat-focused build is going to open with a potion or strong attack, and whittle away with bursts of 2-3 quick attacks. Punctuate with parrying, counters, dodging, an aard, or run like hell away. Fall back on quen if completely surrounded to get out of the mob, instead of rolling like a clown. Then repeat. You have to be patient, because one or two hits will kill you in your light or medium armor. You can't just hold X to win with this build. Roll if necessary to get away from flying enemies, or a shaelmar, but don't spam it for cheese
