I realize this isn't art but I want to hear some opinions.
I changed how a boss gets its i-frames; before, the boss had a meter that filled up when taking damage, and when it got full the boss was fully invulnerable for like 15 seconds, which didn't feel too great. I then experimented with a stamina system for the player, and that felt far too limiting.
Now, there is a damage proration mechanic. Basically, the boss can now technically be combo'ed indefinitely, but any subsequent hit in a combo deals less damage than the last, and if the damage gets too low, the boss simply ignores it, which ends the combo. At the end of the combo, the boss gets 2 seconds of i-frames, regardless of how long the combo was. This by far feels the best out of these 3 solutions I've tried, but it's not communicated to the player in any way; the boss might as well be ignoring damage randomly as far as the player is concerned. That's why I want to know if I should continue with this mechanic, like maybe add a combo counter that makes it clearer to the player what's happening.