The help file for berserk reads:


BERSERK 'FURY OF THE CLAN'
Syntax: berserk

Only powerful warriors can master berserking, the ability to enter
insane rage in combat. Its effects are not altogether unlike the
frenzy spell -- a huge surge of combat prowess, coupled with a
disregard for personal safety. Berserking characters are more
resistant to the effects of spells, however they suffer a penalty
to the effectiveness of their skills and spells/supps/powers.

Orcs who use this skill in the midst of combat against a powerful enough foe
will get a short-lived burst of additional offense. They will also make an
additional attack in the following combat round, and possibly in subsequent
rounds.


Does this mean warrior class character who use berserk get MORE resistant to spells?

>Does this mean warrior class character who use berserk get
>MORE resistant to spells?

Mostly, yes. Berserk is a solid bonus to most saving throws. Mental saves (which are much more common for songs than spells, but there are a few exceptions) see a penalty instead.

In game advice contradicted the helpfile, thank you for confirming and clarifying what they likely were referring to.