"Oh, cool, you have your elemental synergy on curve, really nice." - Any pirate warrior after the un'goro patch.
Elemental synergy is crap, that making you to play cards when you don't want it. Even if you will use a firefly to trigger elementals you have 1 less mana each turn, that you spent on bad stats, when you wanted to clear the board or kill key minion, like Gadgetzan Auctioneer.
i think this is a little bit worse than Netherspite Historian just because it's more expensive, i mean you can usually run 2 netherspites to have some early game and fix your mid/late games with her battlecry but this is alreadya mid-game card, i can't think of wanting to run more than 1 of this in my decks because he's a 5 drop that has 4 mana stats( well kind-of, he's not a 7/7 nor that pterodactyl adapt thing that can become a 7/7)
This card makes conserving the elemental trigger across turns very easy. For example, if you played an elemental on turn 6, and found there wasn't a good reason to play something like Blazecaller on turn 7, this card can let you keep that trigger rolling into next turn and gain value for it. Firefly also keeps the elemental trigger rolling quite well, but its value is so low in comparison.
As for what one can discover, shaman has several high value options and one dud in Dust Devil. Mage, priest, and even paladin (so far it's only Ragnaros, Lightlord!) can typically expect a solid class card from this. Neutral cards have duds in Magma Rager and Arcane Anomaly, so it's almost guaranteed there's at least one elemental of good value. I suppose that means it's only natural the saltiest players in the world will consistently hit the trifecta of Dust Devil, Arcane Anomaly, and Magma Rager as their discover choices.