Crafting gold cards is never a waste. Especially when it's something that gets lots of use, like Dr Boom or Sludge Belcher.
The only time I crafted a gold card was Piloted Shredder, and it was because I already had one, AND the card gets SERIOUS use, AND it's almost like a two-for-one since the card that pops out is also gold, AND it is only a common. But then I managed to unpack a gold Shredder just today, a couple months after I originally crafted it. Soooo... yeah.
If I was to craft a gold card at this point it would probably be Sludge Belcher. But maybe the next expansion pack comes out with an even better taunt and Sludge Belcher falls out of the meta since the 5 slot is so crowded! If I crafted a gold Boom I would half expect to open one in a pack later. This kind of stuff is also a concern with regular cards, but with gold cards it stings even more since they're so darn expensive.
I think so long term with this stuff it's killing me, lol
My goal is to have a complete collection and I've slowly been catching up to it with the way I've budgeted myself. Maybe I should just start banking arcane dust for the next expansion and see what happens then. At the rate we're going now we'll get another major GvG level expansion around September or so.