Melee AND Ranged Magic DPS Debuffer (Anything close? Cabal Force Blader, which the most closer thing to a spellsword class to ever grace the mmorpg realms).

Strenght: He uses a few spells from affar, mostly to land proper debuffs, then he gets in and fast strikes for low damage, low TP/MP cost but for lots of hits that combined with the debuffs and self buffs stacks into a good damage that also favors others DPSs. Weakness: Weakness would be that consumes both, TP and MP, and also that his DPS would be dependant on skill/spell speed over main damage stats as critical or determination. No defense at all, maybe a sightly evasion buff but thats it. No xskill with tanks.

A general idea? imagine someone who uses MP to land spells with debuffs in them for lower DPS than a bard from a range, then he transitions into a faster and more combo complex class than MNK that hits for a little less than MNK itself and can`t burst like a DRG, while taking advatange of those debuffs and then having to retreat to debuff again. Instead of buff or DoT managment, he will have to do Debuff managment, as he changes his position from the outside to the inside of the battle.