Well, since you have paid the cost of Hard Choice (Spot Aragorn), couldn't you play it even if no companions with the Aragorn signet exist? You don't have to either spot a companion with the Aragorn signet OR a "healable" companion.
Right, but the issue for me is what happens after you play it. Let's say you have two companions with the Aragorn signet, one with
Black Breath and one (wounded) without. Given that you're to complete the effects as much as possible, why can you choose the companion who can't be healed?
To do this, it seems you
are doing a form of targeting before "complete the effects as much as possible" kicks in. Which was the impression I had, but I'm not sure how to back that up. With
Rout for example, targeting is merged with the effects--if you have a companion who is exhausted and another who isn't, you must choose to carry out the effects on the companion who isn't.