How about having a fifth daily task that is always just to do 3 dungeon battles the reward doesn’t matter it could be 50 gold or 1 soul it’s just there as a reminder.
I have a better idea.
Why not have the little green exclamation mark on the games button?
Just to remind that there’s something to do (except treasure maps), like bounty, pet and dungeons.
I like your idea.
I try to remind my guild to do the dungeon each Sunday, mostly so I never forget. However, a button blinking or giving me a (1) icon under games, like with keys, would be awesome.