First off, I only have 1 copy of
Thorongil, and he's committed to my Gondor Kings deck. Also, Elessar gets the 9 strength after 5 pool of cost.
Isildur's Heir only gets it if he plays another card, and the Gondor token cards all cost more than the 1 pool difference (except
heirs of Gondor). Admittedly, I generally do get
Heirs of Gondor out, but I also use tokens from that card at a higher priority than exerting Boromir when I need to beat a minion.
Also, since I start with only 2 companions (Boromir and Isildur), if I get swarmed before
Halbarad or Aragorn come out, then
Isildur's Heir cannot use his defender ability. I used
Isildur's heir for a while in the aforementioned Kings deck, and I really don't feel like he would fit in the Boromir deck. Also note, I just added 2
Banner of Westernesse and took out a
Dagger Strike. I feel like Elessar could use a Banner well, and most of the time's I've used him, he either winds up beating a bunch of swarm minions or tanking against the really high strength minions.
Just a note however, I play house rules, and we typically do not use adventure decks, so it's also not like I can use a site to get Aragorn out on the first turn (This mostly applies to getting Aragorn out before Isildur has to skirmish)