Sorry for not answering yesterday. The website was down for quite a while, and I'm living in CET. :(
I tend to agree with you, 4% Miracle feels like more of a game changer than 2% Luna. Though I don't blame anyone for using specific fathers because of preferred hair color! :D
I'm trying to balance the team out, that's all.
Kellam!Laurent: M/C/Luna/Aggressor
This unit deals more damage when he gets to jump on the opponent in player phase. (This will be 'enemy phase' in the eyes of our opponent).
Libra!Yarne: M/C/Vengeance/Aggressor
This unit deals more damage when engaged upon and surviving until it can retaliate. His Vengeance does virtually nothing if he gets to jump on the player, but in that case, Aggressor should ensure that the player takes a least single digit numbers of damage, which might be enough for a different unit from our team to engage the same player unit and kill it with miracle/counter/attacks.
Of course, this guy doesn't benefit from Aggressor on enemy phase (like every other unit with the skill) but if he miraculously survives with low HP, then he'll immediately become a big threat. Especially in the 'player phase' of our team afterwards.
Laurent is more reliable and stable, Yarne is more volatile, chaotic and has greater potential, but at the cost of lowering his chances of doing anything at all (Luna at full HP > Vengeance at full HP).
As you can see, the thought behind it isn't too elaborate, I'm just making up random scenarios.
Yes. I expect their survivability to be around 5% with the Book of Naga, so they might be able to do something with it (Vantage).
In this case, I agree with using a skill asset. It would also help out hit rating a bit. If one does not care about losing 6% Vengeance, then they can go with a luck asset.
It's a matter of how you want to stack your rng. Not perfect Vengeance will result in a few more percent Miracle. I'm unsure which one is better since there are arguments for both.