It is not currently possible to use Heroic Leap after using Goblin Rocket Jump. The tool tip indicates rocket jump should prevent other effects which slow the rate of falling but I don't think the general player would see heroic leap as that. You can also use rocket jump after using heroic leap so I don't think it makes any sense to prevent this.
Other effects which slow the rate of falling cannot be used within 10 sec after using this ability.
I'm adding this as SomeChanges instead of bug since i found old wowhead comment:
Description
It is not currently possible to use Heroic Leap after using Goblin Rocket Jump. The tool tip indicates rocket jump should prevent other effects which slow the rate of falling but I don't think the general player would see heroic leap as that. You can also use rocket jump after using heroic leap so I don't think it makes any sense to prevent this.
I'm adding this as SomeChanges instead of bug since i found old wowhead comment: