To clarify, I am currently sitting on 54 standard packs. With Alterac Valley Expansion right around the corner, I wanted to know if it would be more dust efficient to be opening my standard packs prior to the expansion packs or vice versa.
I am trying to complete my collection from all sets. Currently I own every standard card card with majority of the wild cards, just dusting up the epics and Legendary cards that are missing. I have pre-purchased both bundles that blizzard offers for Alterac Valley and sitting on 145 packs of those, wasn't sure on which would be the go to route.
Thanks to any replies <3
p.s. I know I spend a lot of money on this game, I literally play no other games besides this because It's readily available on my phone when I feel like playing something when I am taking care of my infant son. I am spending my money on something I enjoy so save me the lecture about money management.
If you really want all the cards, it doesn't matter too much whether you open expansion packs or standard packs. Because of duplicate protection, you always get cards you haven't collected yet. If you want them all, it seems to me that standard packs are better all around, since you have a chance of opening cards you don't have from the older expansions as well.
The real decision point comes in if you're not really expecting to get all the cards, then you would want to think about which expansion has cards you're missing that you want more, that are played in more decks, etc. In that case you could target those expansions' packs instead of going for the diluted pool of standard packs.
I'm also the type that wants to get all the cards, and my technique since the standard packs came out is to only buy standard packs, other than expansion pre-orders and discounted bundles. My gold is going 100% to standard packs. For me, I always dust the nerfed cards, so buying standard packs give me a shot at filling in commons and rares that I dusted in the past that may someday be useful (or un-nerfed). For example, I'm still hoping to open up a couple of Swords of the Fallen, since the card is playable even after the nerf, but I never re-crafted it.
As far as the situation where you literally have already collected every single standard card and you didn't dust any nerfed cards, it's still better to wait on your standard packs. After opening 145 Alterac Valley packs, you're guaranteed to get all the commons and rares, and extremely likely to have all the epics already, but there's virtually no chance you could have all the legendaries (unless you craft a bunch of them). So your standard packs will only give you Alterac Valley legendaries - 54 packs would average out to 2-3 legendaries so you're better off opening those after the new expansion launches.
edit: I looked up the epics and there are 25 of them -- but you would want 2 of each so actually you wouldn't have all of those even after opening 145 expansion packs and 54 standard packs. But you would be close. Epics are about 1 per 5 packs so you need around 250 to get all of them.
Be aware that if you haven't opened standard packs before, you will also be eligible for a legendary in the first 10 packs you will open. But the legendary card may be from any of the Standard extensions. :)