Why not considering making a Single Player game like Heroes of Might and Magic or Warlords 3 Batlte cry, something inspired by that, only using this art style?
I really really like this game, it kinda reminds me of some old games I used to play in 2000s.
Now that being said, let us get down to suggesting on this game shall we?
First, I think the artifact and champion getting system needs to be improved.
It should be an option that, for instance if I sacrifice 10 or so artifacts of 5 stars I can get one 6 stars.
I also think we should be able to have a system where we can sacrifice a certain number of champions (you choose them) we can get ANY champion we want!
As long as that champion, of course, equals the same rarity level as the one that we are sacrificing, so I do not say we sacrifice 10 commons and get Cold Heart or Arbiter or something.
The "New Player Game Rewards" should never end IMO, and if they are not going to give new champions (which is logical) they should give stuff like energy and skill tomes IMO.
The Faction Wars battles should replenish their skill tome (at least rare ones) in those boss battles at least a week or every month or something to make them farmable.
Also I would like to see more single player content, either a new clan boss or a new campaign?
I also have a crazy IDEA where, DAILY quests rewards are reset the moment you finish them so you can do the same things as with weekly and monthly IMO.
Please note that some of these may not be 100% thought through, it is just to give you the basic knowledge of what most (from my opinion and experience) players want and find flawed in your game as it is.
I will still continue to play this game and, most likely advertise it for free, however I think you may have created something thas has greater potential than it is currently being realised, so think about, some people are pissed off by the lack of energy...perhaps we can give them something to do every day, slow but sure, but still leave nice epic bonuses for those who, khm, keep the game running?!?!?