I've been playing solo to learn this fascinating game, with a view to introducing it to my gaming group. However, I've run the Down the Anduin quest 14 times and only come within sight of success on 1 occasion

I'm using Eowyn for questing, Prince Imrahil for fighting, and Aragorn for a bit of both, with a 50 card deck made from the starter set, and the 6 expansions of the Shadows of Mirkwood series.

Unless multiplayer is somewhat easier than this, I'm not sure the game is going to go down well with my group to be honest. We are all experienced gamers, having played MTG, and Warhammer Quest the Adventure Card Game for example. Am I just rubbish at this game, or is it really so hard?

(apologies for the double post, but my connection is misbehaving )

The game is hard to be sure, especially with nothing but the core set and a few expansions. However, Journey Down the Anduin is not a quest that uses any unfair or gimmicky methods to beat you, and you can definitely build for it. What I mean is, taking the deck you've thrown at it 14 times, its starting threat is 32. The Hill Troll has an engagement of 30, so you're taking a troll on turn one before any cards are even up! So you'll probably want to find a way to be below that. Multiplayer in that quest is going to be a bit more forgiving I would say though, since only one of you will have to deal with the troll. Each quest is unique, some are easier multiplayer and some are easier solo.

_{Multiplayer is sort of easier for the harder quests, because you can reach all 4 spheres of influence and can therefore use much wider range of questing/combat techniques. As Chris pointed out - you can't have Threat level that high in this campaign, because the Hill Troll engages your right off the bat with no defences what so ever (what can you summon with 3 starting resource tokens, right?) So if I were you, I would start from that - changing your heroes to ones with less Threat level, so you get few rounds of breathing room.}

_{What I like about this game the most is the versatility of the deck - you said you've played it 14 times. Surely you had to notice, that some cards are more/less usefull than others. (i.e. if you play Spirit deck, the guides can help you get rid of all the locations in staging area without having to travel there) + You need to build for combat, so reduce(meaning kick out) defenceless allies and less-useful Attachments or Events. Since this campaign is more fight-oriented, I'd recommend Lore for its healing power and Leadership/Tactics for fighting - when we played, I had Legolas with 2 Blades of Gondolin, so everytime he killed an enemy (which was every round, since they are spawning so rapidly), he placed 4 progress tokens on the quest...}

_{There is a thread answering your question about difficulty in solo/multi, it really depends on setup, the core set is more coop-friendly, the newer sets are more unforgiving and harder in multiplayer.}