It breaks my heart to hear that the rewards will be removed.
I tried to do the challenge dungeons for a long time with little success. I think our team managed to get 2 gold coins and 2 silver? It was difficult to perform on a low-end hardware machine.. and getting a good team together was just.. horrible.
We spent money fixing up players with gems and enchantments, taught them the fighting patterns only to get them to quit on the team because they would find it too hard. This happened many many times and eventually the team gave up.
At the back of my mind, I always thought it would be something we could try again in the future.. but now it seems impossible.
I honestly wish they left the current structure as is and moved on to creating a new challenge/reward package in WOD.
This way the rest of us could catch up eventually.