-reduced damage from explosion to random classes

No good justification for this.  Why should these roles take _such_ less
damage from explosions? If they're going to huck fireballs around, _be
careful_.

idea from Spork, see
https://github.com/Bulwersator/CopyOfSporkHack/commit/2b5a1fabb68e8d40b29ff2e53e311e6031d38484