Yes, the rewards vary based on the nature of the task and the difficulty. I don't remember exactly what I got for those, but I think it was 3 or 5 glory keys for the first one and then 10 gems for each of the 2nd and 4th. The reward for the Zhul-Kari task is always maps, probably 4 if I remember correctly (another reason I wasn't in a rush to do it).
I had "Win 75 battles" on Sunday and got 30 gems for that. Win 8 or 10 battles with troops from Whitehelm gives 40 glory. "Change your armor" give a gold key. Use a gem key gives 5 gems. A bunch of the 1st slot tasks,
which are usually quick and easy, give 2000 gold. Some examples are "win a battle with the _______ banner", "win a battle using 3 troops from ________", etc.
There is a pretty wide variety. Some days you can finish 3 or 4 tasks in 20 minutes, and some days things don't line up at all and it would take a couple hours of dedicated play to clear them all. Yesterday was a good day.