Well. Fencing uses 1 handed swords and agility. If this one uses great swords, i don't think they could call it a fencer or any form of the term.
I think they mean they fence with the runes... In that they parry the mobs strengths... However in ffxi the only way to use just a sword is two handed...
Also great sword is the only non A+ weapon for a job.
bst isn't A+ in axe, katana isn't A+ for nin... just sayin'. No job is A+ in club or staff either.
Also DW isn't always the best option. You need enough natively or sub to make it worthwhile. Goes back to the joyeuse example on cor. Better to single wield it, than DW it with something else.