The scroll of Antimagic isn't a spell. Its like a potion if I remeber right, so it COULD be done as fast as any spell. If Antimagic thing is cast on a mage with ANY spellslike effects upon them, they are immediatly cancled, and the mage cannot cast more spells. Heck, since we are starting the whole thing awhile in advance for the mage to use triggers ect, the cleric could cast one on himself, then use one on the mage. Done. Mage can't do anything.
I'm pretty sure you can dodge ADHW if your fast enough. I've done it alot. Running out of the area is rather cowardly, but one must do what is neccesary.
The cleric could also use some helper spells that make tensers transformation look like the armour spell.
There are times when a mage could defeat a cleric, and times a cleric could defeat a mage. Let this bikering part end. It doesn't accomplish anything, since none of us are about to say that we're wrong.