If you are serious about 19 mages, make a horde... the deal is stack fire damage, spec frost, freeze and then melt face

Heres my recomeneded build.

Lucky Fishing Hat, +8 spell damage
Scout's Medallion
Talbar Mantle
Feyscale Cloak +70 armor
Inferno Robe +150 health (Yes its a 35+ item)
Crystaline Cuffs +9 Stamina
Serpent Gloves +20 Fire Damage
Keller's Girdle
Darkweave Breeches +35 Spell damage / +20 stamina
Nat Pagle's Extreme Anglin Boots Boar's Speed
Lavishly Jeweled Ring
Advisor's Ring
Insignia of the Horde
Arena Grand Master

.... of Firey Wrath (1h Sword or dagger)+30 Spell Damage
Pulsating Hydra Heart
Banshee Rod of the Sun

that is all, with that though, your looking at roughly +150 Firedamage.