So I have done a number of Clue scrolls of varying difficulty because I am always after that elusive third-age piece. I have noticed some things I personally find to be irritating and also don't encourage me to continue my treasure trails.
#1 - Rewards
Too often after completing a Hard, Elite or Master Clue Scroll you get rewarded a very small amount of coins, in fairness clue don't take very long to complete. However, getting 20k GP as your only reward for an Elite is... a little disappointing. Perhaps having GP rewards scale such as 50k - 500k scaling with clue difficulty. I also have noticed many clue caskets only giving 1 item rewards, such as coins. Not sure if that one is intended or not.
#2 - Clue Trading
I think it would be really cool to have an NPC at home that will exchange 1 of each clue for a Master Clue (As they are a little rare to get). In addition, giving this NPC to instantly complete any tier clue by using it on him once per day I think would also be a cool touch - you could even capitalize on this and perhaps make it so that every time you vote you are given 1 "Clue completion scroll" that will instantly complete 1 clue of any difficulty.
#3 - Collection Log
I have also noticed if you receive a reward from 1 tier of clue that is also a part of the rewards for another, it will automatically fill in. Example: I got gilded plate legs from a hard and they show on my collection log for Elite & Master as well. (I'm not sure if that's intended).