For clarification, do you have the Master's Strike ability at all? If so, is Goblin listed in the examine window of that ability? There isn't a separate ability for each different creature. As you complete Lore and Legend quests, the new creature is added to the existing Master's Strike ability.
JanEQ is correct, it should be listed in your Knowledge book combat arts. It is named "Master's Rage". You'll find goblin is now amongst the races the spell effects. ~ Kaitheel
