+Hp -Def Hardin?

You should fodder him off for bold fighter.

Even with a defense bane, Hardin's still a good unit. Steady Breath is a good A skill for him, and the only way they'd be wasted is if you don't actually use him after giving him the skill.

You honestly can't go wrong with IVs on this guy. Hardin can make use of all of his stats. That said:

If you plan to pull for a new Hardin with better IVs, don't inherit yet. Bold Fighter is a fantastic skill, and you should fodder Hardin off if you're not using him. If you inherit and then fodder him, you'd be wasting the equally rare and powerful Steady Breath.
If you're fine with this one, or you plan on merging him, go ahead and inherit. He's one of the best units in the game regardless of IVs.