The randomness in game play is simply too stingy. Some options.
-rare chance in high level normal levels
-guarantee from high cost gem buys
-forked quests where you can choose a path to chosen rewards
-player item trading
-guild item trading
-item conversion (lower star upgrading to higher star)
-choose a ‘value’ of rewards from a titan defeat that is lower than a random draw
Another idea that is random but may help us is a build que in a forge that has a chance at an ascension item (like is done for hero training)
I am sure there are others but that is a start based on collected suggestions and some added.