I've played two games so far - one 1-quest game and one 3-quest game. I played with Enclave996 both times which is why we're likely to be posting similar comments.
Some comments on the game so far:
1. Unless there are some mechanisms for player interaction that I haven't discovered yet, the game is essentially multiplayer solitaire, with the only significant effect of the other player being that you have to "race" them to the finish (so basically, they just serve to put a "clock" on your own gameplay). I've only played 2-player games so far, but it doesn't seem like adding a 3rd or 4th player would affect the game much other than to increase downtime between turns.
Multiplayer solitaire games can sometimes work, but almost all the good ones involve players taking their actions simultaneously so as to minimize downtime (e.g. Race for the Galaxy) or alternating micro-turns very quickly (e.g. Dominion) - and even then, your actions have at least some impact on other players, even if it's just denying them access to resources.
In my opinion, this game would benefit greatly from some sort of cooperative gameplay mechanic (competitive mechanics don't really make sense given the theme). As an example of a game that handles this sort of thing relatively well, I would point you towards "Legendary - The Marvel Deckbuilding Game". Each player drafts cards into their deck from a common pool, so the players have to plan together to make sure that everyone is getting cards that synergize well and that multiple players aren't competing too heavily for the same card types. The players then have to cooperate to deal with threats that, if left unchallenged, will harm all of them and will eventually lead to everyone losing - but at the same time, players earn victory points for the various heroic deeds they perform, and the player with the most points at the end is the winner, thereby preserving both competitive and cooperative elements.
So my suggestion would be to add some kind of "players against the board" system where events and monsters will eventually start to harm the players if not dealt with. Players can still earn VP for addressing these common threats, but are forced to cooperate to manage them to prevent game-over. This would also allow you to diversify the different characters' powers more - it currently feels like everyone just has different ways of getting good at combat, but with a diversity of threats you could have specialized problems that a certain character is better at dealing with than the others.
If you're willing to consider major mechanics overhauls, you might also want to look at the way actions are selected in "multiplayer solitaire" games like Race for the Galaxy and Puerto Rico. In these games, when a player selects an action, all players perform that action, but the player who picked it gets a slight "perk" - optionally, other players may then be unable to select that same action in the same round. This reduces downtime while simultaneously increasing player interaction and strategy (because you can indirectly inconvenience your opponents by choosing an action that benefits you more than them).
2. The game feels much too easy thus far. Players can start pulling their best cards out of the "Development" pool immediately, meaning that after a few turns of developing and charging up, combat against all but the toughest opponents becomes so trivial that it's almost yawn-worthy. Another negative effect of this is that the players draft all their coolest cards right at the start, and then get progressively less interesting card choices as the game plays on. You want the progression curve to go in the other direction - the player should have a constant sense of building up and becoming more and more powerful, not a huge initial spike in power followed by diminishing returns for the rest of the game. Overall, the game is sorely lacking in a sense of tension or stakes - the only urgency is created indirectly by the need to "race" the other player.
3. I haven't played enough games to be sure of this, but the game feels like it still has some balance issues. The quests you draw seem to have a huge influence on how likely you are to win - in our last game, I completed two twelve-point and one sixteen point quest while Enclave996 only ever saw 8-point quests, making it almost impossible for him to win. Particularly as the more valuable quests didn't seem to be significantly more difficult to complete than the cheaper quests. The second balance issue is with the characters. Again, I haven't played enough to be sure of this, but of the two characters I've played as (Dandelion and Yarpen), Yarpen seemed to have a definite advantage. Both need to power up cards that they bring into battle to assist them, but while Dandelion's "special" action generates two coins (and thus two power-ups), Yarpen generates two power-ups AND has the option of an almost-guaranteed investigation token, or money, or moving a curse flag. Admittedly, Dandelion has the advantage that he can power up his cards without spending an action IF he can find an alternate source of money, but so far I haven't found a reliable way of doing so, so on the whole I'm tempted to say that Yarpen's ability is just better. Again, though, more plays are needed to say for sure.
4. The music is too loud and rather repetitive. A volume slider would be appreciated - as is, I'm just playing the game on mute.
5. When selecting your first quest, the button that allows you to look at your character's details (including the "exchange rate" for investigation tokens -> proof) doesn't seem to be accessible. This is a problem for new players - if you don't know or can't remember your character's "exchange rates", it will be harder to compare the quests to know which ones will be easier for you to complete.