This is really neat. It's about as epic as Final Fantasy would be if they'd get out of their holes and would write a story that doesn't jave holes every half gaming hour and is conclusive.
I mean jsut take a look at XII for example - grand battlescenes of soldiers hitting each other with pointy sticks (no blood - wait what?) and a HANDFUL of mages total. Game starts and the first thing on the license board is White Magic I, you only have to acquire the license to use it, implying that everyone in this world has inherent magical skill (enough to cast Flare).
So why don't we see epic battlescenes like that? probably because the animation of suck scenes would take to long. The engines are probably too rigid as well (still waiting for the first FF (non-MMO) where changing armorpieces changes how your srupidly-dressed-spikey-haired-protag onist looks like).
Back to the video - it was pretty amazing how you pulled the animation of the spells. You just saw those spells deflect and know it's gotta be shell, or the clock-animation being haste - courtesy to Square here for having at least one consistend thing (besides the name Cid).
The only question I kept asking myself is which magician-type class would be cool enough to wear a Katana (Bluemages wearing sabres etc). Then again in XII you can do that, and nothing is set in stone with FF (xcept for Cid).
P.S.: Was that Bahamut w/ Mega-Flare?