I thought the fight is actually okay. Not extremly hard but also not easy.
Played with a friend and we used the pregen chars. 1 Rogue ( Human Male ) 2 Handed Warrior ( Elf ) + Red Prince and the Mage ( Human Female ).
Red Prince had Leadership maxed ( + 10 Initiative ) -> Mage was able to cast Hail Strike and freeze Alexander.
The Rogue could easily kill the Mage. If you cant kill him fast just bless someone and the meteorite spell becomes worthless because fire becomes blessed fire -> burn becomes holy fire -> you get healed by the mage.
Use encourage and you should have enough HP to survive for atleast 1 Round and just heal.
As soon as Alexander has no Armor you can just CC lock him and the worm wasnt a problem.