Thats just the risk you run by using him. He is powerful but he needs a down side.
Well, a lot of people build dream cards like that. Excessively powerful but with a major downside. Personally, I prefer balanced cards that aren't necessarily too powerful but have no downside, but there are certain characters who should be bipolar.
Boromir is one and Denethor is another.
But as I look at this card again (which I really like), I am thinking about some other options for it...I'd like to see a line about him being twilight -1 while you can spot two unbound hobbits (Merry, Pippin, Boromir, RB)...maybe at the expense of the Enduring, Ranger, and killed lines. So it would be:
While you can spot two unbound hobbits, the twilight cost of Boromir is -1. Unbound hobbits may not be discarded or returned to hand.
Response: If Boromir is about to take a wound, exert 2 unbound Hobbits to prevent that wound.
I still think I like your card better, but that's just a thought so you could start Boromir, Merry, and Pippin.
-wtk