So on a PS4 with main game+HoS+all patches (currently 1.11) my toxicity level of 246, I take three 70 toxicity level Decoction's and bam, my Vitality is going down every second, I'm poisoned! Is that normal, that's 210/246 toxicity?!
Yes, that's normal. You're in overdose threshold which starts at 75% of max toxicity and in that state your health goes down. You can use Heightened Tolerance skill from Alchemy tree to increase the threshold up to 100% so you're never in overdose state and can use all toxicity without any vitality loss.
