1. Make the game more competitive!
Winners should receive prizes on their account. For example, on server end, if a player have been in winning team - reward is 50 gold. If player was duke - 100 gold, and if he was king 200 gold. Also if alliance, say 50% of winners. These are examples only, management should decide. For now we are "just playing to win".
2. Introduce gold buying "defense mode"!
There are servers with "no night attacks", which is OK, but the earth is round enough, and time zone difference makes "night" in America - day in Russia. Instead, allow player to buy " 300% defense for 2 gold, for 8 hours", but - this is important, any player can turn on "defense mode" only once in 24 hours! Also, you may introduce item from cards that replaces the 2 gold. As before numbers (300%, 8 of 24 hours and 5 gold are just examples)
3. Make more 3/3/3/9, and remove 1/1/1/15
1/1/1/15 gives too much power. Remove that, or let that be only WOW