They need goals that you can spend a little time each day making progress towards an end goal.
Something along the lines of doing only portions of a raid zone. Like a zone with multiple caves you need to explore through, but you can enter at certain points. Stuff like this will allow you to do the seperate parts as you have the time, but still give hardcore players a goal to work towards. They'll just be able to get the rewards quicker because they put more effort in, but still allows casuals like myself to play and make progress over time.