So I'm a new player who can't wait for the rotation to happen. As part of the preparation I crafted Baku, to add it to my collection and possibly play it in the future in Wild (or dust in the future). Now I'm almost out of dust and I'm wandering if I should do the same with Genn and/or epics that I'm missing. I could always dust some of my extra cards (worth about 1k), some of the weakest legends (like Face Collector) or legends that will be rotating out (Val'anyr, Skull of the Man'ari, Professor Putricide).
You'll probably get mixed advice with this, and I certainly cannot see a strict right or wrong answer here.
But I would say not to. You could view it as doubling the dust value of each card provided you spend half of it on the rotating cards, but that's still a net loss (2 x disenchant value = 1/2 crafting value). Genn allows you to do a few things but so too would the cards you dust, and they would probably open up more options overall.
if by dusting extras you mean 3rd copy of a card, go fo it. I do not unders why some people do not do that at once. if you mean dusting cards you only have 2 of, do not do it as it will be really bad value.
If your have 3+ cards surely dust them to get hof cards that gives you extra dust and there is not much chance any particular one gets nerfed (unless you think they might get nerfed then don't dust)... If by extras you mean cards you don't use but you have only 1 or 2 copies of, then don't do that, you lose more dust than gain.
In my opinion you shold dust extra cards and if you dont have enough dust to craft Genn, you should open some packs (I know we are close to new expansion) , last thing you should do is disenchent cards that you need... I made a video about hall of fame cards: https://www.youtube.com/watch?v=Z0-VMYRSKm4 But i think you already understand how refund works :P but still if you have time you can watch video :)