Breakthrough skill is one of those cards that have a short expiration date. Good now, totally useless really soon. If you have some good old forbidden chalices or even fiendish chains stick with them. You wont see any major difference.
This box is only good for those who like ddds, shs and childish fluffy animals.
And yes, it will certainly become a meta box. But not for breakthrough skill.
why break skill will be soon useless ? I think chain will be obsolete faster than break skill, because can't be used 2 times, and monster negation is stronger than attack negation