What are some decent, balanced quests to run when you want to test out a new deck/concept?
i.e. No strong gimmicks or shenanigans designed to be played a specific way, with a healthy mix of combat and travel (gods of random chance permitting).
Deck-Test Quests
If it starts high threat, Journey down the Anduin.
If it doesn't include Lore, A Journey to Rhosgobel.
If it is a monoTactics multiplayer support, Foundations of Stone.
If it pretends to turtle and lets enemies in the staging area, Into Ithilien.
If it is a Háma lock or Dúnedain deck, Battle for Laketown.
If it draws a lot, The Fords of Isen.
If it a Damrod trap deck, Intruders in Chetwood.
If it uses Erestor, Road to Isengard.
If it depends on high level of synergy of the heroes and player cards, Escape from Mount Gram.
If it doesn't defend that much and destroys enemies quickly, Shelob's Lair.
If it doesn't handle locations that much, The Fate of Númenor.
If it struggles to quest quick enough, The Drowned Ruins.
If it uses an insane amount of threat increase, The Passing of the Grey Company.
If you don't like to play with other people, The Siege of Annúminas.
Sarcasm.
Just played Across the Ettemoors and that seemed like a good candidate; mix of enemies & locations, and you can manage it's gimmick through the encounter cards (you don't need to bring your own healing, though it would certainly help).
Was able to get a good feel for how the new deck performs in practice, and promptly throw it in the bin 
My personal favorite is The Ring Goes South. That's probably my most played quest.
Passage through Mirkwood or bust
Yep, Passage through Mirkwood. If the deck even stumbles with this one or losses against it, you gotta look real hard at the deck and see what's wrong with the deck. Then for serious testing, Journey Down the Anduin. These two decks are in the Core Set, unlike the other quests which you might not have.
Edited by ppsantosHummerhorns.
I'm only three cycles into the game, but my first go-to testing quest is Massing at Osgiliath, followed by Into Ithilien. I lean towards a one deck to rule them all style (though I make multiple decks frequently, I just try to build them so they hold up against anything). And if it can't beat those it's not going to hold up when the going gets tough. If I really think a given deck might be pretty weak I'll start with Nightmare Passage Through Mirkwood, which is the right a mount of difficulty that I can see the weaknesses of my decks.
I don't really feel that there's a solid all in questing quest within the first three cycles. So I might use Into the Pit or Redhorn Gate, but those are generally pretty easy quests, so they don't tell me too much besides my capacity for willpower.
Massing at Osgiliath for solo, Assault on Osgiliath for coop. Then the usual: Anduin, Return to Mirkwood, Fords of Isen. But mostly the LotR saga ones are the best.
Journey along the Anduin - Allrounder Classic
Foundations of Stone - I would only use it for solo deck testing
Peril in Pelagir - Battle Questing might look gimmicky, but the quest enforces equal amouts of attack and quest power.
Fog on the Barrow-Downs - Again use this one solo
A Knife in the dark - Balanced quest; you can choose (more or less) if you want to trade nasty effects for combat.
The Ring goes South - Questing, fighting, Location Control.
Intruders in Chetwood - To check out how you do against sidequests.
The Wastes of Eriador - Allrounder, but one of the longest quests in the game.
I use These quests as they have no gimmicky mechanics (for me) and don't Focus to much on questing or combat. The last 4 quests have objective allies or heroes. They don't really Change the gameplay much and I think you can see very well, if your deck does work or not.
Helm's Deep. The quest challenges your quest ability and your combat ability at the same time. That's really your fundamentals there.