This Extreme buffs have CD`s, and their duration is not so great.
So it`s only active around 20% of the time.
Like 10 sec per 1 minute.
It`s great if you have a burst-caster type of characters, but...There`s not so much DEX-related casters.
Even same INT arti isn`t OP as current meta chars have channeling-related skills, so someone like QSJ\Ruby will not even give their full combo.