I've been dying for a chance to discuss Witcher 3 build stuff for a while now, so buckle up:
That's a great start. In my experience, Light Attack builds are superior to Heavy Attack ones in almost every way. The heavy attack animation takes twice as long to connect, and does twice as much damage, so against an unmoving target (more on that later) damage output is identical between them. Even after investing the full 20 points for each tree, damage output is basically the same, which seems to have been intentional on CD Projekt Red's part.
But fast moving enemies are much more common than slow ones, and some of the toughest enemies in the game (like vampires) are very difficult to hit with heavy attacks. So that alone is a massive advantage for Light Attack builds.
And the Cat School Techniques talent (which doubles your Crit damage) is way better than the Bear School equivalent (which just increases your max health by 20%).
So you'll want to max out the first 3 Light Attack talents, and ignore the Heavy Attack tree. On an initial playthrough, the 4th talent (Crippling Strikes) is OK. Especially when used in conjunction with Poisoned Blades, it's sometimes helpful to be able to dodge away and recover for a bit while your DoTs wear a tough enemy down. But the bleed and poison talents have some significant drawbacks. First, they'll supercede any bleed or poison effects on your weapons, which kinda sucks (they don't stack). Second, and much more importantly, they don't scale. 5/5 Crippling Strikes does 125 damage/ sec, which can be decent on your first playthrough, but when you start critting for 5-10k per swing, it's just not worth 5 points. I think you'll be better served by skipping the bleed/ poison talents and immediately getting stronger talents instead.
In the Defense tree, Fleet Footed is incredible. Might be the single best talent in the game. Dodging in Witcher 3 is similar to Dark Souls, in that there are some complex mechanics behind it. Some attacks can't be dodged at all, some can only be dodged in the attack's outer range of effect (80%+), some can only be dodged in a certain direction, etc. Fleet Footed basically gets rid of most of those modifiers so that unless you try to dodge directly
into an attack, you've pretty much got iframes during the dodge animation. I haven't found any of the other Defense talents to be worth the investment though.
In Battle Trance, Resolve and Razor Focus are worthwhile, but that's about it.
In Alchemy, Heightened Tolerance and Acquired Tolerance (along with Metabolic Control in the General tree) are critical for boosting your Toxicity high enough so that you can run multiple decoctions. Ekhidna and Ekimmara give you a ton of life-gain within combat (the former by refreshing Quen, and the latter simply by doing damage). Water Hag is the only one that's decent at boosting your damage. I use Arachas as my 4th for a bit of extra damage mitigation, though you won't be at that point for while.
Until then, you have to stick to Potions popped right before battle. Swallow is great for increasing longevity (though it's best to think of it as a buff to food effects in combat, so make sure you're using it that way), Thunderbolt and Maribor Forest for extra damage, and Tawny Owl for stamina regen. Though once your healing is covered by decoctions, you'll likely drop Swallow from your rotation and prioritize Tawny Owl, as you can easily turn extra Stamina into healing.
Other talents worth taking in Alchemy are Protective Coating, Tissue Transmutation, Synergy, Killing Spree and Hunter Instinct. Fixative was the last one I took, but it's mostly a quality of life thing.
The only one I haven't mentioned yet is Cat School Techniques, which is another good candidate for best talent in the game. 1 point for +20% Light Attack damage and +100% crit damage is huge value. It does require that you use only Light Armor (until you unlock the Levity enchantment from the Runewright, afte which you can wear whatever you want), though if you've got Fleet Footed and are dodging properly, it's not much of a drawback.
This is my current build at level 87, and I think it's pretty close to optimized:
ALCHEMY / COMBAT - EUPHORIA
You're in good shape if you're rolling out of White Orchard in the Temerian Armor with the two crafted Serpentine swords. You'll likely find a few relic items that are better in Velen, but I used mostly that setup until I started crafting Feline armor. Crit chance and crit damage seem to be the best stats to maximize damage output, so I'd recommend switching to the Ursine swords in your 20s. Glyph for Quen in your armor, Svarog Runestones in your weapon (until you can get Severance from the Runewright), and you should be good until you reach Toussaint.
