[st.patrik]

this could be a typo - but you said the orders were to 'attack rearmost' which would mean that he would never fire his weapon, but instead attempt to get in melee range.

A lot of spells have a range too short to be used - I don't know if that was the problem with the Shadow Blast.

One pretty nice (unresistable) spell is 'Gifts from Heaven', if you have the mages to cast it. It has poor precision, so don't expect to hit first time, but if it hits it does 150 damage. A few hits later the Wyrm is dead.

One approach that may work is to try to overload the target with fatigue. Stellar Cascades is an Astral spell which creates fatigue (I'm sure there are others too) which is easy to spam (assuming you have Astral mages)

BTW, even if your guy fired, if may not have had any effect, since the Ethereal Crossbow involves a MR check, depending of course on how strong his MR is.

It really depends on what nation you are playing, what strategy to adopt.