I have a few suggestions. For the promo pack in the corner, maybe lower the cost of crystal? That would cost too much money to actually acquire. Also, I would suggest maybe some sort of Talent point system, or something that could allow you to customize your hero. Maybe a hero creator that would cost gold to do, maybe like 50k? Just a few thoughts.
An easy way to beat cave 5 is by using: Witch, Mermaid, Succubus, Black Knight, Goblins, Magic Cannons. Spells: Phoenix Strike, Comet Shoot, Healing Wave, Zeus Wrath, Hercule's Strength, Athena Protection. Of course, you need to use Grimtooth while he has max (3500) mana. That little invincible goblin is annoying!! >_<
 "Epic War Saga"){kind=icon}
 "Epic War 3"){kind=icon}