I've been toying with this idea for quite a while, and personally I like it, but it often happens that what I think is great and brilliant, aren't exactly the best idea, especially because I know how things are designed and should work, but the player don't.
This particular problem comes in form of a boss fight, that I kind a want to be a challenge in a different way.
Many boss fights, taking care of the adds, minions of the boss, is priority 1, because they tend to be weaker and faster to kill, lowering the amount of damage everyone is taking.
I want this particular boss to be empowered when the player kills an add, say add a flat +20 to all stats, which lowers over time with 2 per round, and give the boss a stacking poison effect, so the more adds the player kill, the stronger the boss gets, and the more damage the boss takes from the poison like effect.
The boss will regularly ress fallen adds, or call in new ones if all are alive, which in turn will reapply the effect when killed again, making the fight about managing adds and not get overwhelmed, but also not just nuke the living out of everyone.
The player will be informed about this through battle events dialogues, and a save point will be conveniently nearby.
As the topic tittle says, feedback is welcome, also any concerns about this.