I sometimes bring a seerstaff high mage just to kill of the pendant of kaeleth.
Having played dark elves and high elves since the time of maiden guard (happy face) I always rate BG as a threat. Mine always take banner of murder (cheaper razor standard) but in a vs. HE list ASF is vicious.
With the 300 point fire mages, you can only cast fireball. Pretty much every fire spell is pretty crappy and the fireball spam that takes advantage of this is like the coven of light - expensive, gimicky, and pretty easy to shut down - just subpar.
A high elf archmage gets +5 to dispel, which means if you throw 2 die, I can throw one. Risky - maybe but I have a fallback level 2 so it isn't a huge loss. If you do 3 I'll throw 2 and stop it pretty reliably. In the end, 30 repeater crossbowmen would be more reliable and much more scary - and count as core.