So what is your favorite potion mix?
I've heard that it's possible somehow to drink potions regardless to their toxicity, but only those combos valid here which remain in the maximum allowed toxicity level.
Apperaently the green and orange marks on the bar have no effect at all.

I usually use these:
White Raffard's Decoction (+hp, - dmg)
Swallow (hp regen)
Rook (+dmg)

I have the catalist skill at level 2, unfortunately it doesn't reduce the "White Raffard's Decoction" potion's damage penalty as it should be. If I hadn't play on insane i wouldnt use this potion, but it helps to have 800+ hp at the begining of act 2 :)

Virga
Rook
Gadwall/Tiara/potion of your choice

Obviously, with lvl 2 catalyst.

EDIT: with tiara as 3rd potion, toxicity exceeds allowed level.

This is my favourite combo on Alchemy tree (keep in mind I have significantly reduced penalties from talents):

Thunderbolt + Rook + Whetstone/Oils + Berserk skill = 290-300+ damage on heavy hit. Seriously. Add Greater Power Mutagens in all slots and you're looking at 320+ damage per swing.

Gadwall + Swallow/Virga to compensate for lack of defense.

Edit: From what I've seen, except being useful for Alchemists, toxicity has no obvious effect. I've seen no difference in stats when "intoxified" as a Signs or Swords build.

On alchemy (or alchemy+sword) build:

Swallow (+2 vit regen, no side effects)
Rook (+17% dmg, no side effects)
Wolf (+27% incineration/bleeding/poisoning, no side effects)
Golden Oriole (+47 resistance to incineration/bleeding/poisoning, no side effects)
---
it fills up whole toxicity bar but you still can drink it... add some oils and alchemy adrenaline buff and whoa ;)
plus with impregnation and few greater crt effects mutagens (+6% each) almost all trash opponents die in fires while bleeding from poisoned wounds, lol


On dragon fight:
Virga (+305% resistances, +32% armor, -1 (one! roflmao) % critical effects)
Rook (+17% dmg, no side effects)
Gadwall (+3 or +4 vit regen, -6% dmg) - i think in next playthrough i'll go with swallow instead... I found that I didn't really need that regen.

All with taster lv1 and catalisis lv2

I played very recklessly on my alchemy build. Here's what I usually chugged down

Thunderbolt +32% damage
Rook + 17% damage
Swallow to counteract the reduced vitality from the thunderbolt

Throw in an oil (20-30%) and the +30% for being poisoned and berserk mode well...things died and quickly.

I intentionally avoided things that put me at a defensive advantage. I liked playing on the edge :D