Caster's limit break is almost same than physical ranged, both are AoE attack.

So, why don't change that ?

Caster can be able to use DoT attack, most poweful potency than melee (to compensate for not being immediate damage).

So, some idea for visual:
-Summoner when use LB summon multiple poweful primal for few second
-BLM change the weather in battlefield for few second and lightning storm will cause dmg in the target

I know that maybe changes have already been made, but I still decided to share this idea