No, you cannot heal unique minions, or it must be part of the gametext. Like some Enduring nazguls, some conditions and events. Other than that, you cannot heal by discarding another copy. I'm very sure about this, allthough I cannot back this up with parts of rulebooks and such. This is because I can't open either rulebook, as they can be found in Archives in Minas Tirith....
And about those cards, if you want to use their text, you must show as much cards as you want to use. For instance, if you want to make a minion less strong with
Cirdan, you need to show as much events as you want to use.