It's clear in the Korean version of Maplestory that Cannon Overdrive is increasing the damage specific to what the description of the skill states, by 50%. I hypothesize that in Global Maplestory that Cannon Overdrive is actually adding +50% damage, which is added to Boss Damage % and Damage %, resulting in a much much smaller overall increase.
I hope this is enough information regarding this bug in order to get it fixed.
Steps to reproduce:
Step 1: Use Revolving Cannon or Rocket Punch on a target with 0% damage and 0% boss damage
Step 2: Record damage with battle statistics.
Step 3: Review the damage dealt with Revolving Cannon or Rocket Punch.
Step 4: Repeat steps 1-3 but this time, use the hyper skill "Cannon Overdrive"
Step 5: Repeat steps 1-5 but with more %damage and boss damage
Step 6: Compare results. Cannon Overdrive should reflect a 50% damage increase for Rocket Punch and Revolving Cannon.
Character name: Jucking
Character level: 253
Character job: Blaster
World name: Reboot
Date and time of the incident: Anytime after patch v205 came out.