Hearthpwn

is it worth to disenchant him?

Do you play Elemental Mage with Frost Lich Jaina? If yes, then it might be worth keeping. Otherwise, the answer is "probably"; consider how potentially useful he would be, then weigh that against the potential of whatever Legendary out there you do not own that tickles your fancy.

Golden card of dubious value is always a disenchant.

Maybe trial with it a bit first.

If you have frost Lich Jaina, keep him. He's really fun in that deck and can give you tons of healing. Otherwise, dust him and craft a legendary that you really want.

Primordial drake is still better in my opinion

Well it's a non broken, classic Legendary, so it will never rotate out. It might not have been a Tier 1 ever, but I'd say it is still a useful one. With Frost Lich Jaina it shines in sone decks, and it had seen some better days with Enrage Warrior. I'm seeing it being good in some other decks again in the year to come.

Now that I have most of the useful classic legendaries, I'm thinking about crafting this one myself, so that day might come for you as well after 2 years of Hearthstone. The golden one is kinda cool imo.

I'd keep it for now, mage got some elemental synergy in KFT so there's definitely a possibility for more in the coming expansions, not only for mage but also for shaman.

That was my first golden legendary 2 years ago and I still have it today it falls in and out of usefulness it is worth keeping though imo.

iIf you're a f2p don't DE it, never DE a classic legendary with a unique effect even if it's not a meta card, I remember when I got a deathwing and DE it, I regret it until now!

ATM it is only used in elemental mage I think.
It was a very much used anti-aggro card in Controll Warrior back in the days.
Some expansions ago a lot of people suggested to disentchant Black Knight because this tech card will probably never be used. This expansion it was quite good -> A card like Geddon which was allready good a few times will probably also have it's time again.
It's basically an anti-flood deck card. It allways was especially good against Zoolock (and I think this card will come back in 1-3 expansions too since it only needs 1-2 good cards to be very good)

keep, it's playable few month every year, better to have it

Baron Geddon tends to be outside the meta most of the time. If you want to play competitive and have another legendary or some epics you still need  I'd say dust it.