At the rate the devs are going, a large majority or heroes will never, ever have epics. If there is a new hero every month and a new epic every what, three months, there is a problem. There are two relatively easy ways to fix this.
-There could be two epics made for every new hero, maybe on a scale of a month or two.
-Big Fish could take a break from new heroes for a couple months(2-3) and focus on outputting a ton of epics.
Once you get all the heroes there isn't much to do except get materials for runes and epics. Having more epic choices would make that late game a lot more fun and long-lasting.
Please consider these options @Joel @Joveth