Because of Tamiel's absorb HP and MP attack in universe he is a bit harder to take out then normal. Try Bacchus / Myuria / Faize / Edge, give all of them max HP boost, or at least Bacchus and Edge then use Bacchus to continually Blindside Tamiel, that should keep him from doing to much raid wide damage.
From there just keep unleashing rush combo's as it's a safe way to take him down (with the large boost in rush guage increase he will be in rush mode quite often, so getting free combo's in will help your healers.
He is somewhat succeptable to stun still though, so having Bacchus melee him can help wonders. Not much else I can think of to help though, GL.
Inside the symbology menu in the battle menu you can disable any spell you do not want cast by pressing 'X' (X or Y, it says at the top of the screen which one for certain) You can tell it's shut off because the spell will be grayed out and the green 'ON' button will be darker then the others.
Likewise, this can also be done from the main menu, go to Skills -> Use Skills and turn them on / off there.
So far I haven't received the game yet, being in Canada I'm a day behind your release dates. With any luck I should have it later today if not then tomorrow morning. I'll try to track down a strategy guide as well to help with the raw information, and once I get it i'll start on the battle trophies for you.
You bought the SO strat guide, right? I am going to work on the monster guide first. I might be able to finish it before I leave work, already done the first 30. Could you work on typing up the battle trophies?