Once you've unlocked a skill, it's available to all of your heroes (for that character). ..... oops, I just noticed that you seem to be misusing the term "Hero". Heroes are player controlled henchmen, not your characters.
So, yes your Hero character in the second campaign will have to capture the skill itself, or use an Elite Skill Tome.
Last edited by Quaker; Jul 28, 2012 at 03:10 PM // 15:10..