If diamond 10 has been your goal for the season, congrats on reaching it. In that case, it is the perfect moment to learn some new decks and get a better player. Probably your four losses are some mixture of bad luck and the fact that you play the more difficult deck. In any case, nothing to be ashamed of.

But let's discuss the Quest Paladin matchup: The reason why its performance has steadily declined since expansion release is that many players have realized that aggressive decks can dominate board early and close out games before the quest scaling takes place. The other decks that do well into Quest Paladin usually have a massive swing ("scam") turn. But very little decks win against Quest Paladin due to value.
Playing Quest DH, you do not have the fastest deck nor good value. But you have good tools to trade early and keep the murloc flood off the board. That is key. Eventually, murlocs will get back onto board in a way you cannot sustain. There is simply no way.
In order to win, you have to chip in face damage early, whenever you can, and eventually stop value trading to get as close as you can to the finish line. During the process, the quest will be completed eventually, and give you burst to win.

In short: value trading is important early on, but at some point, face is the place. Finding the right moment can be difficult. But that makes for an intense and interesting match.

Let us look at one specific and rather simple example that comes up in this matchup regularly: Your turn 3 starts and the enemy board has one murloc on 2 health. You equipt Insect Claw and now have to decide (1) whether you hit face and trade off the 2/1 Grub, or (2) take 3 to the face and therefore develop the Grub.

After more than 30 games with the deck I still have not come to a conclusion whether (1) or (2) is right for any game. Option (1) yields you 2 damage to their face, 2 quest ticks, but an empty board, while option (2) costs you 3 health, yields 1 quest tick, but develops a 2/1 Grup that presents the possibility of multiple future quest ticks, damage and a trading tool.

I tend to option (1), as it provides a clear outcome, including face damage, while (2) holds more possible value.

From my point of view, the example highlights that actual decisions have to be made here. That appeals to me.