Blizzard just announced a welcome change to Hearthstone card packs.
Starting with the next expansion, a legendary opened in a pack will be one that you don’t own but from the same set. Once you already have a legendary in gold or standard version, you won’t get a duplicate of it until you have the full legendary set from that particular set. This change will go live from the next expansion but apply to all card packs. There’s also a change to non legendary cards. You will never open more than you can use in a single deck of any card in a single pack. So no more 3 or more for rare, common, or epic cards in one pack.
The final change to Legendary cards is that you are guaranteed a legendary within the first 10 packs of a new set. To celebrate these changes, Blizzard is doing a promotion right now that gets you bonus Un’Goro packs when you buy the fixed sets.
7 packs +2 packs = 9 packs total
15 packs +5 packs = 20 packs total
40 packs +12 packs = 52 packs total
60 packs (only on PC) +18 packs = 78 packs total
Hearthstone: Heroes of Warcraft is available on iOS, Android, macOS, and Windows.
Source: God is Geek