Upon further reflection, and this may have been raised by someone else before, it seems to me that the underlying purpose of class quests is:
to get us to grind longer and harder;
to force us to collect as wide a selection of heroes as possible (if this hasn’t occurred already), to cover all combinations of classes; and
by virtue of 2 above, to make us even more desperate for ascension materials.
That’s a fairly smart tactic from Small Giant because it means certain heroes that would never otherwise see the light of day might actually get ascended for the exclusive purpose of farming class emblems (especially in the case where a player is lacking heroes for a particular class quest).
I can already foresee that I am going to struggle with class quests involving Rangers and Wizards.
Whether or not it turns people off (especially new players) is another thing entirely.
Should be an interesting first few months.