Another potential problem with the current system is the Reactions of NPCs. If enemies will have Reactions too (I don't know how it is in D&D but I think they should), it would be too easy to exploit them because of how predictable they would be.
That makes quite a bit of sense. It wouldn't be great for enemy AI reactions to be predictable, used on the first attack no matter what, and that means coding the AI to be smart about the reactions. And if the AI is smart about how it uses its reactions, it would be quite annoying for the player's reactions to be dumb, always used on the first attack no matter what.
