Well, I tried to play 'Passage Through Mirkwood' solitaire this evening, just to see how it would go. I figure that with its difficulty rating of '1', it would be a good warmup for trying some of the more challenging scenarios.
First, I tried two games using just the Tactics cards. Gimli, Legolas, and Thalin, with the Tactics cards from the core set plus the first couple of Adventure Packs. Couldn't even get out of the first quest area. Starting with 3 threat means that you'll almost never get any progress right away, given the starting location and Forest Spider, and if you run into even a small rut of locations, you're done for (the monsters you can fairly easily kill, thankfully).
I figured, hey, let's try something else. Let's go with the Leadership cards! Aragorn, Theodred, and Gloin took a crack at this quest, and despite handling themselves better, they didn't make it any farther.
Next time I give it a shot, I'll probably at the very least take an actual constructed deck, with cards from two supporting types. My mono-color decks certainly don't fly solitaire, haha.