Quick note, it’s super niche situation but of spell hunter takes off (semi-possible with the new hunter hero) she’s a good tech for aggro decks to run. Once again, super specific and probably won’t ever be worth it unless spell hunter is the next odd paladin of the ladder.
Simply put, unless dusting her before duplicates and other golden cards you don't care for will be the thing to make you get what you want from Rastakhan, then there's no reason to dust her yet.
You might get something that pulls her without the battlecry (like an Oaken Summons thing) and then she's greatly stated.
You also have all legendaries from Boomsday, I'd say you're someone with resources and probably can get most of what you want. You can probably wait a bit more. If you can do this without dusting her, all the better, and who knows, I remember seeing lots of people saying that Twig of The World Tree, Togwaggle, Azalina and many others were all safe dustings because they would never the light of day, much less be competitive and we know how that turned out. I'd say it's still too early, and if you can afford it, could wait a bit more.
It is a terrible card, but I got her in golden aswell and use her in my golden legendary shaman deck - she is actually not that bad always - pretty good against control to hinder them from playing big minions for a turn or 2.
I always give cards a few years before I disenchant them. At least let them rotate to Wild. Have they not proven strong enough for Standard for 1-2 years then they won’t break Wild either.
Second: I always play a golden legendary at least give times before disenchanting it. It will not drop in value if you play it a few times. Unlike real world items such as cars, TVs, playing cards etc.