Wasn't it actually that the enemies who attack the person (who uses missile weapon) with the melee people get +4 bonus to their attacks, not the 4 add or take the THAC0. Basically you can stand 2 steps away from each other and shoot from the bows and be OK, but when one switches to sword and another continues with the bow, then the one with the bow will start getting hurt.. Or something heh...
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