Is it possible to complete most, if not all the scenarios, with one static deck and maybe a sideboard?

The way I approach Arkham Horror LCG deckbuilding is to create one deck only from that cycle's campaign. Is that viable in this game (or even including the entire card pool)?

Also wondering how you guys test decks? From what I read, LOTR LCG seems more "game-y" as it seems you have to sometimes build a deck specific to a scenario to defeat it. Right now I'm tweaking a deck against the 2nd core set scenario and getting stomped so just looking for some advice.

Seastan actually has a deck on ringsdb that had beaten every quest available at the time solo in nightmare mode...There might be other decks that could do the same.

https://ringsdb.com/decklist/view/8682/the-one-deck-1.0

As far as the second core quest goes...if you have a giant card pool, there are a lot of decks that should be able to beat it. With a small card pool it is a solid challenge. When I first beat it I focused on low threat and solid questing to give myself time to build up a board state before having to engage the hill troll.

Adding to what Trialus said, if you want to keep up with your habit of only using cards released in the campaign (or in this game's case cycle) check out "A path less travelled":

https://darklingdoor.wordpress.com/2017/05/30/new-series-path-less-traveled/

Seastan and maybe others also have some youtube videos playing quests in minimal purchase mode, where they beat quest only using cards from the products needed to play the quest (aka core set, and (if needed) a box expansion and/or AP).

I guess I should mention that I only been playing one handed and maybe that is why I'm getting spanked...

4 hours ago, Markspinner said:

I guess I should mention that I only been playing one handed and maybe that is why I'm getting spanked...

One handed is my favorite way to play solo and you can definitely win, you need power decks especially for some of the harder quests. Or if you prefer a more thematic experience play on easy mode or just starting with an extra resource and then more heroes/decks become viable then just he too handful of power ones.

21 hours ago, Markspinner said:

The way I approach Arkham Horror LCG deckbuilding is to create one deck only from that cycle's campaign. Is that viable in this game (or even including the entire card pool)?

Possible? Yes. Viable . . . ? Only if you're a veteran.

19 hours ago, Markspinner said:

I guess I should mention that I only been playing one handed and maybe that is why I'm getting spanked...

When I am testing decks (playing solo), I also play 1-Handed Solo. I use Passage Through Mirkwood (Core Quest #1) and Journey Down the Anduin (Core Quest #2) as the benchmarks. That said, I don't necessarily look at these as things a deck has to "beat" solo in order to be a good deck or even a good experience. Even my best decks probably average about 50/50 against the Anduin River in 1-Handed Solo, but a deck can show off its chops even in a loss to that quest: how were it's starting hand draws? How was it's economy in the early rounds? What did it do well? What did it struggle with? Were there any cards/combos that seemed really useful, or some that seemed to be useless? These all give a better and better picture about a deck and can help tweak and refine it.

While the game does an overall admirable job of scaling up or down for the number of players, some quests are just much harder in true (read: 1-Handed) solo than with two decks. The Anduin river is one such quest. In 1-Handed, players are responsible for 100% of a Hill Troll, versus just 50% in 2 Player (or 25% in 4-Player). Same goes for Stage 2B, where you reveal an extra card. In one player, that means 2 Encounter Cards per player. In 2 Player its only 1.5 cards per player (and only 1.25 cards per player in 4-Player).

It is possible to solo it (and it's a great feeling when you do), but I'd encourage also finding a mindset that can find a lot of value and enjoyment in games that are losses as well (I certainly have almost as much fun playing whether I win or lose).