5-star units are completely unstoppable at lower levels usually due to their unique “legendary” weapons and their higher Mt. value. It levels out slightly when you hit the max.
Pretty much all new heroes released lately though have a boosted stat total that was previously reserved only for “Trainee” units like Donnel and the child dragons (Young Tiki, Fae and Nowi). “Powercreep” is word that’s growing more popular on fan sites. Guessing this is par for the course for these gacha games?