As always thank you for the development updates Marco - tbh an interesting wall of text can be better than a picture in my opinion. Anyway, making the passive easier to activate is definitely better than buffing individual spells. That being said I also feel like increasing Bacchanalia's activation threshold, for example to 2/3, is a more elegant solution rather than allowing the character to reach 40k hp.
So Food is right, but not for the reasons he gave. There are two problems with allowing the blood zon's life to overflow.
1) The life available to the amazon who wants to enable her passive. If you play by getting ~30k hp for example, then focus on dmg, an active Bacchanalia gives you 20k effective hp pool. If you play by overflowing your HP then you have a 32.7k + effective hp pool.
2) Allowing life to overflow dumbs down the playstyle of the build. The reason for this is that it is harder to keep your current life at a set fraction of your max, than at max. You have to cast Balefire and get just enough life after each kill that will enable you to stay as close to 2/3 of your total life pool as possible. The closer you are to two thirds, without going over, the better you are at playing the build.
On the other hand, by playing the life overflow strat you essentially remove this gameplay mechanic. You don't have to manage your life after each kill stat based on your max hp pool - you just get as much of it as possible. Not to mention that if you overflow and are close to the 32.7k threshold it would be optimal to stop using Balefire all together. Only after you have a decent buffer above the overflow value, for example having 40k hp, can you start efficiently using Balefire again without risking losing the passive bonuses.
Thus I don't see the merit of increasing Bacchanalia max life bonuses and enabling the overflow playstyle. Because if it is in the game, then after the character reaches 120 we might as well rewrite the text on the passive to: "Blood magic - when you overflow your life". The overflow playstyle is clearly superior to "keeping the life under some fraction X" playstyle.
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Mana cost increases could be an interesting way to give powerful abilities downsides. This one is hard to analyse without playing the game, so I am looking forward to seeing how it works out in practice.