A fun card, but also one of the most difficult cards to use well. It can generally be frustrating that the staging area attack shenanigans (This, Dúnhere and Forth Eorlingas!) are so difficult to pull off, but that's actually quite fair if you observe how powerful they are if you succeed, since you completely avoid the need to defend and handle shadow effects from that enemy before killing it. It's like a free Feint every time you do it.
That being said, this is, again, a very difficult card to use well. Like Forth Eorlingas!, it's a combat action, so the enemy needs to still be in the staging area in the combat phase. It's explicitly called out that no other attackers can join in and help you so you need to stack all that attack power on a single hero to get the kill - made more difficult by the fact the Bow is restricted. And it requires a printed Ranged keyword, which sharply limits your options, disallowing options where you might play it on anyone with a Dúnedain Cache or Rivendell Bow. Let's examine these limitations one by one.
Enemies need to still be in the staging area in the combat phase. There are three ways to achieve this. Firstly there's the straightforward standard option of simply keeping everyone's threat below enemy engagement costs. You can manage this to some extent simply by carefully picking the quests you take this strategy against, since some quests have noticeably higher engagement costs than others. Otherwise you have to have good threat reduction, such as The Galadhrim's Greeting, Double Back etc, and preferably start at lower threat. The issue is that in multiplayer you really need to co-ordinate with everyone on this. The other approach involves messing with enemy engagement checks. Pippin increases enemy engagement costs, as does Take No Notice, Anborn or ally Mablung; while Fresh Tracks, Noiseless Movement and most notably Advance Warning can stop enemies making engagement checks at all. These options have the advantage of working in absolutely any quest (unless the enemies are immune to player card effects) but it's still going to take some careful deckbuilding, possibly co-ordinated among multiple decks. Finally you can push the enemies back to the staging area with effects like A Light in the Dark or Ithilien Archer. It's worth noting that none of these relevant effects appear in the sphere from which the Great Yew Bow hails (Except I suppose Secret Vigil for threat reduction).
Need one super-powerful attacker. Since the Bow is restricted you can only have one more restricted weapon to boost attack. Remember also that the Bow exhausts to do its thing, so no matter how many actions your hero has they can only make one staging area attack (unless you give them a second Great Yew Bow, but then that's both restricted slots used up). So realistically the most we can expect is perhaps 6 if we use say Legolas with Great Yew Bow, Bow of the Galadhrim and Rivendell Bow (which is handily not restricted). Enough to get some kills, but there are a lot of tougher enemies out there, and we want to kill them as well, right? Wouldn't want them being left out. So how can we get more? Well the answer would lie in non-restricted boosts. I mentioned the Rivendell Bow, but we also have the options of Dúnedain Mark, Keeping Count (though this is another difficult one to use in itself), Gondorian Fire and some one-shots in the Black Arrow or events like Unseen Strike (which fits since you want to stay below engagement costs anyway). Definitely some reasonable options to consider here. There are also a couple of helpful possibilities in hero choices as well, which I'll cover in point 3.
- Printed Ranged. That restricts your options to: Legolas, Brand son of Bain, Bard the Bowman, Hirluin the Fair, Faramir, Haldir of Lórien and Faramir again, plus the currently unreleased Lanwyn from The Thing in the Depths. Brand can't trigger his ability since the enemies aren't engaged with anyone. Haldir it's pointless unless you want to stack up and have him make two pre-emptive/staging area attacks each round. Faramir will have more difficulty mustering the necessary . Legolas is an OK option as I covered above, but this card seems specially made for Bard and Faramir. Bard's ability means that he's effectively 5 against most enemies, and then you could boost him to an effective 7 with a Dagger of Westernesse. Meanwhile Faramir gains for enemies in the staging area, so apart from the ones you're having him kill any enemies you just want to ignore or leave sitting on Ranger Spikes will help you; he also has the Gondor trait for Gondorian Fire, though if you want to go that route you could then also consider Faramir since he sphere-matches Steward of Gondor to stack up resources for Fire. And of course all these could then be combo'd up with some of the other non-restricted boosts I mentioned for number 2. Still, that's only 2 obvious picks, with a couple of options which would be good once you get them stacked with attachments. And the two obvious choices both have a starting 11 threat which you'll have to contend with while keeping enemies in staging (though obviously you can manage, if your other two heroes are Hobbits say you could still be starting as low as 23).
All in all, the Great Yew Bow is, without wishing to sound like a broken record, a very difficult card to make good use of, with some difficult limitations to work around. On the other hand, the power and fun factor of staging area attacks should not be underestimated if you can manage to jump through all the necessary hoops, and there are definitely more viable options for using it than people may think. If you have dismissed this card in the past then I would say it may be worth reconsidering it and taking up the challenge of making it work. It can be done!