You need to make it so that each of the hits in every 5 hits are calculated independent of each other. For example, making it possible to do 69 damage with one attack (5 energy). Right now, It's only possible to do 50, 55, 60, 65, 70 and 75 damage.
Before the change to 5 hits in an attack, the average damage was 12,5 over ALL the bosses, regardless of how much or little health they had - now, not so much.
The sample range is so much smaller now (5 times smaller, to be exact), that the average is fluctuating from 10.5 - 14.5 (yes, it's really that much). This makes it incredibly hard to predict how much energy is needed for a boss fight, and it also makes it a problem for people using diamonds to refill. In some cases, you might need to buy 200 diamonds to beat a boss, the next time you beat the exact same one with the exact same stats, you might need 150 or 300. The worst part is that there is no way to know until you've already spent those diamonds.
So please, make it less inaccurate by plainly randomizing a number between 50 and 75 instead of doing multitudes of a number between 10 and 15.