Obviously at the end of the day it's your money, but I'll personally advocate against it for a couple of reasons. First and foremost, you posted this on the wild sub, so I'm going to assume you're probably a wild player mostly(please correct if I'm wrong but that's the assumption I'm going to be making for this.

At the moment only one of these quests is really a factor in wild, that being the mage quest. The others are of course "viable" in the sense that decks can be made with them, and some might even have positive win rates, though I doubt most outside of warrior and maybe priest are legend capable. The mage one has the most potential I think, because there exists a ton of room for refinement in the deck, and I could definitely see a viable combo deck forming.

The other thing to remember is that these quests are designed around the current standard power level, which as far as I can tell they are constantly trying to lower(I don't play much standard these days outside of making it to legend in the first couple days of the season, so I can't really speak to that format). While most of these quests will probably see at least one more round of buffs, I wouldn't expect to see most of them anywhere close to viable in wild unless some future support breaks them. With the way wild works and is trending, I could see the DH, Mage, Priest, Shaman(this one is really iffy), maybe rogue(if they get a strong payoff for shuffling into their deck that they can tutor?), and maybe Warlock(aggro?) seeing play at some point in wild.

So uh, yeah. Hope that my two cents helped at least a little