I tend to agree with you about the pardon power, but it should be remembered that governors have them too. Given that, we have to consider it a form of executive action, I think. Not monarchical. Just a power sometimes given to political executives (I believe the pardon power exists in other countries as well).
I do think the American understanding has a significant flaw, whether or not I agree with pardoning at all -- and that's the idea that pardoning is inherent in the notion of sovereignty. As I understand it, the drafters in Philly included a pardon power because they thought it was an inherent power of a state, whether monarchy, republic, democracy or whatever. And so that gives us this expansive notion of pardoning, and thus the idea that it is final, absolute, irrevocable, unlimitable, and per SCOTUS this summer, inviolable. That seems wrong.