Not Gold, Purple! Epics are harder to grind for because there are so many per Class and trying to get a specific one(s) you need is hard.
At only 1 or 2 Gold cards, you’re sure to make Gold well before all Purples for a Class.
Edit: UNLESS they finally introduce scrapping and Gold scrap at 25% coins, which would be 100 coins = 1 Purple dupe. Best of both worlds right there!