I don't bother with the HB for Hero Purchase. I always use Shards and Gems 2 Legendary and 1 of them duplicate. 4 elite with at least 4 duplicates and 3 ordinary with 1 duplicate. Mostly from gems a few from shards. I have gotten a few jellies but no more than 3 when i use the gems.
Using HBs for heroes is only good in the beginning where it's hard to farm even 40 shards for a basic hero like Marksman. When I first started playing iOS I used rolled HBs a few times to get an Engineer and a Marksman, rather than slowly farm shards for them
Slimes get fed to my heroes so they can at least have lvl 2 skills