After playing Corey's list last night I don't think that a level 4 archmage is the way to go.
Well, i'd almost say it's like comparing apples to oranges when comparing these magic setups. I'll get to that in a second, but first i'd like to point out that magic got off three drain magics in the game, which is really what I was gunning for. With those drains and my available dispel pool and 3x scrolls, your magic wasn't a bit theat. Now, I know your list wasn't magic heavy, but rolling 6(?) single di castings a turn for raise dead, that can be pretty potent (damn bats). PLUS, I didn't roll the best spells ever.
Now, I say apples to oranges, because the way I run that tournament list is to get the optimal magic for the least amount of points. I don't want to rely on magic, but I want to be able to at least do a little damage/support the rest of my army. That setup only has 6 PD, and the bound ring of fury, with 3 scrolls and 4 DD. This allows me to cast 2 spells a turn with 3 PD, or split it up into 2 and 4, WITH the looming ring of fury. Against certain armies he's more of a Drain Magic battery, but again, for the points, he does what I want. I also did not have the banner of sorcery, which he does have.
Now, his setup is incredibly heavy magic. With the Archmage and Dragon Mage casting, he'll be cracking out between 8 PD(11 when you cound the Dragon Mage's free PD for each spell) and 11 PD(14PD with Dragon Mages free PD for each spell) depending on how he rolls for the banner of sorcery. Also, the archmage's spells have a very good chance of being irresistable (any doubles on a SUCCESSFUL casting roll). So the magic phase is really gross.
So while my magic last night wasn't big and flashy, it wasn't supposed to be. It was supposed to get me reliable magic defense without wasting points on little scroll caddies...and I hate that my ring of fury couldn't kill 3 ghouls in that last turn
That being said, if you are going to take a Dragon Mage, i'd really suggesting playing with him a bit to get the hang of him. When I ran with him, it took a couple of games to figure out how to get the most out of him.