Part of the problem is the lack of updates and thought put into the Challenges/Mountains rewards. A level 110+ hero needs 150k XP to level up which means 100 purple XP pots or 20 XP Decanters... With 40+ heroes the drain is huge... The same goes for the gold required to keep your heroes Skills up to date !!
The Mountain needs to give out FAR more XP and gold.
The Challenges are just silly... We have to go to a lower difficulty to get the items we most desperately need (Tiara, H.Banger, Boomerang etc) and the gear that's rewarded aside from those we just don't need.
The Challenges need not only a new diff setting but a major reworking of the rewards that is WELL thought out. Thread on this very issue... The Mountain and Challenges needing an overhaul
Another thing to make the game less 'work' like... Let us Raid Challenges and Mountain, all of our attempts, in one shot. That is, let me Raid 2 on Mountain and Raid 5 on Challenges... The cooldown period is just silly. We should also be able to Raid Expedition... Most of us run through it on fast-forward and Auto-attack turned on so why not just let us Raid? This way we can spend more time building our heroes.
We're having the same issue on server 2... It used to be a huge battle for the top 10 in War between 20+ great guilds... Now there are only 5 competitive guilds left and the rest of the top 10 is random each week (guilds yo-yo up and down into the #6-10 spots).
I think these suggestions might help retain so many of the players we're losing... Something needs to be done soon... Please, I hate to see so many folk abandon what has been a fun game.