[Serak Moonblade]

IMHO, the sling and bullets are the best missile weapons. almost all creatures are affected by it. so in a party try to have at least 2 who use slings.
as far as wyrm's tooth (and the rest of the game) is concerned, it would not make that much of difference since the most preferred mode of attack at a distance are area effect spells for groups of bad guys and targetting spells for bosses.

IMHO hold your tanks back till the area is clear of the spell and then charge.

This may not answer your query specifically but may help you as a general tactic.