Hey,

so if I hit myself, do my heroes get to roll defense dice?

Such as:

1) Blast: Do my heroes/familiars that get hit by my own Blast (like Brightblaze, who sadly can only melee, attacking with that Blast rune weapon.. and others around the target, obv., too..) roll defense dice?

2) Dark Charm: Do heroes that attack themselves when controlled by the overlord card "Dark Charm" roll defense dice?

And stuff like this, if there are more such cases..

Yes and yes. Whenever there is an attack (that is, the steps of combat are followed, not a skill that just inflicts damage) the figures affected by that attack roll defense dice. Even if you are both the attacker and the target, you roll both attack and defense dice.

Also, some familiars don't have HP or defences, and so cannot be hit by ANY attacks.