It seems most of us are in agreement that a mobile game shouldn't have a mode that can take an hour or more (including, it appears, the developers)- people who say otherwise should probably be playing The Old Republic instead.
But I think completing 12 battles per day is inherently incompatible with this. Either you make them easy and unchallenging so people can auto through them, or you make them challenging- but then it takes too long.
So the only solution I see is to make it fewer battles- like 5 or 7- or to make it like 25 battles with a 7 day time limit. If they gave the weekly option huge rewards (like almost as much as 7 of the current daily challenges combined) it would provide an incentive for players who start to lapse to at least come back for the GW.
