The idea is great, I like the new mechanic and I like the fact there is some randomness to it.
But sadly, the implementation rather...well...sucks.
My main objection to it is the fact that low-chapter players have almost no use for it at all, as the low number of witch points means one can use only very few ingredients and thus has an extremely low chance of succes for anything, whereas it will be supereffective for end-game players. The balance there is way off.
Near the end of Woodelves chapter and I can put in 9-10 ingredients at the most, with about 66% chance of succes. Meaning it will be much lower for players in lower chapters again. Not exactly a great chance.
The fighterboosters are nice, but with a timespan of 2 hours or so (in my case) it means that anyone who does not have a Polar Bear AND a high lvl Timewarp has almost no practical use for this, or at best near the end of the week for one of the later Tourney rounds. I shudder to think how bad it is for people in chapters before this.
The same goes for the duration of goodsproduction, or coins, or supplies, so short it is hardly worth it, meaning that since you can only brew once a week it is very, very limited.
We only had one week to try so far, but so far I am not impressed. As stated, great idea, bad implementation.