Critical hit rate, unlike how it is commonly defined in other RPGs, is a random chance to deal additional damage only to enemies weak to the damage's element. Because of this limitation, it means critical hit rate is useless against the other 5 elements, making it rather undesirable as a stat, which leads to character skills, weapons, and summons that boost crit rate being observed as less useful in general.
It is unclear if crit damage is able to surpass the observed damage cap.