Yeah similarities are there, but I don't really see it combining two jobs; they do share gauges, but the Spell Fencer needs the Ceruleum Crystal Charged in order to use the magical spells and such; also charging the Gauge increases DPS, and yes, he needs at least 42% to do his "Special Combo."
It's a risk and reward sort of mechanic, as you need Ceruleum charge to cast Magical Spells right? But you also need to output DPS, which also needs the charge.
So, the Mechanic is: Charging the Ceruleum Crystal to fully output DPS.
Thanks for the feedback! I'll change some stuff around later today =D