I think an adjustment to upgrade cost and times for heros would help tremendously.
I've been TH9 since the October update. Since I enjoy participating in Clan wars, I don't enjoy just dedicating all my game play to farming and keeping heros continuously upgrading...
But, on the other hand, it's almost necessary to be competitive at the TH9 level in war.
I think a small reduction in hero upgrade costs and times would make a huge difference in the TH9 experience. Even the slightest reduction would shave lots of time off the completion.



