Cross Class skills and +skill tab items

[Tal]

No.  Mercenaries are affected by +skilltab, +that specific skill and +fire skills (when applicable).  They aren't affected by +class skills or +skill tab.

So, in the case of barbarian mercs, a helm with +bash and +stun would help, and a helm with +all skills would help, but neither the +barbarian skills nor the +combat skills on Arreat's Face would do anything.

Whoops my mistake. Thanks Adeyke. :)