Hallucinate is just better than Journey from Below (or whatever that discover DR card is for Rogue). Hallucinate picks from class cards which are of higher quality than the average DR and you can get spells off of it which is big for Rogue.
And Journey was used in Rogue decks to do something on turn 1. That was generally over taken by the 1 drop Pirate though and then people never really went back to it when Patches came out.
It's a bit surprising to me that people think Fire Plume's Heart is the best quest. Like, I rated it a 3 but I was genuinely close to rating it a 2. I just really can't see it being better than Jungle Giants, Unite the Murlocs or Lakkari Sacrifice.
It's not about judging the quest in a vacuum but how it fits into the game plan of the deck it's supposed to go in.
I think those other quests can be good too but Fire Plume's Heart has synergy all around and fixes some of the issues of Control Warrior.
Control Warrior is very good at handling aggro decks. With this new Taunt variant of Control Warrior that's going to be even more the case. If the opponent goes wide, then they can get Brawled, Sleep with the Fishes or that new 9 mana card with WW. Against aggro you win the match up without even using the quest meaning you can mulligan it away.
Against control decks... the Ragnaros hero power is game winning. It puts a clock on them and gives you more value over them. The fact that you can trigger the hero power FIRST rather than end of turn means you can plan your turn accordingly. Remember that Ragnaros vs Nefarian Tavern Brawl fight? Once Ragnaros got the hero power, Nefarian was pretty much done for and Nefarian had BUSTED cards in its deck and a busted hero power. Now imagine that Rag hero power going against regular decks with regular hero powers.
So CW naturally wins against aggro decks (which the quest is bad against) but CW struggles against greedier control decks (Priest and more specifically Warlock) which the quest takes care of. It's a best of both worlds. You are more susceptible to combo decks though but then you just don't play the quest and just keep armoring up. One of the few counters to this is being rotating out which was Sideshow Spelleater so you don't even have to worry about your hero power being stolen.
The only real way this CW gets beat is by a new, well optimized Midrange Hunter or an optimized Jade Shaman/Druid. These decks can develop big, sticky bodies quickly before the quest becomes active and even if the quest becomes active they can still put on the pressure enough to close out the game.
As far as the other quests go, I think Jungle Giants is probably the next best only because it's so easy to slot it into Jade Druid deck. You play a couple of 1 mana Jade Idols that put out 5/5 and 6/6 that's already putting you towards the goal of the quest. Main issue is that once you activate the quest... then what. Your minions cost 0 but only in your deck so you still have to draw them. Do you play Auctioneer and Nourish in that deck for draw? Probably I would think. You might even play that Fight Promoter card for more draw or the new Scout that draws a card and sets it to 5 mana since you are likely to be playing big minions. You can tempo out the opponent with heavy minions costing 0 but Jade decks already sort of do that with 1 mana Jade Idols.
I was thinking of Jungle Giant in a combo deck but that's unreliable. What if you draw out your combo BEFORE the quest is activated... it will not apply the effect to cards in hand or cards played before. So you would need to have the combo cards in your deck and then quick draw into them. Doesn't seem that consistent so I feel that the way to go with Jungle Giants is to just tempo out the opponent in the late game with flash draw cards... which Jade Druid sort of already does but now it's just better at it.
Lakkari Sacrifice I am now coming around to. Originally I thought that you wouldn't want to play a 1 mana do nothing card playing Discard Zoolock and that is still true.. but you don't have to. If you are playing against another tempo/aggro deck then you mulligan away the quest. If you are playing against let's see a Control Warrior, then you keep the quest and slow roll your opponent with your discards and then the quest reward. A control deck can eventually not deal with 6/4 of stats for free every turn, it's like a Jaraxxus hero power.
I had Murlocs quest as the best one before I saw the more recent ones so I always thought that was a good quest. Just depends on how good Murloc Shaman is in general.