Source: Sub-Reddit discussion on quests that don't require wins make the game more fun
Looking back, I actually find it to be quite true. Logically, the Specific Class quests are more gold efficient (2 wins for 40 gold, 5 wins for 60) but when you don't have the complete deck for that class, it actually takes a while as you might find yourself losing and it stretches out to more than the minimum 2 games or 5 games. I did fill up a Zoo deck with 0-2 cost minions for "The Meek Shall Inherit" quest and it was interesting and fun. The only exception to that discussion is the "Total Dominance" quest for 100 gold, which can be done against the A.I., definitely do those!
Edit: Come to think of it, one exception might be the "Only the Mighty" quest because it involves playing minions that cost 5 or more and that might take a while to pull off in a game.
