Re: IK Berserk Barb
Sorry about that. I thought someone else was going to help on the Whirlwind question.
You may want to use the set, or at least the weapon, for other purposes. When you discover that you need slightly more IAS to reach other breakpoints, sticking something other than a second IAS jewel in the maul will wind up being a mistake. Add to that Fanaticism still helps if, and only if, you go with a Rogue. Of course, you could also Beast a weapon and Iron Golem it with Metalgrid, but wasting a Ber for a SLvl9Fan... eh. You just don't want to unsocket the weapon repeatedly, is all.
Deadly Strike and Critical Strike stack with themselves, then apply one after the other. If you have a total of 80DS, and 20CS, then four out of every five swings DS will trigger. On that fifth swing, you have a one-in-five chance of CS, which amounts to a total of 84% chance to double damage.
If you are absolutely only playing this character within a group, with a charcter who will always be the one using high-end Battle Orders, then you can definitely use a pure build. That's what my original Comprehensive Build Guide suggested, but this means defense would be virtually useless, which is why a single-handed/shield combination was suggested. Pure Berserk uses that, Shout, Howl, and Battle Cry (with a weapon mastery, of course).
Outside of Rogues, if you honestly need range, then the only choice would be an Iron Wolf, but you said you're playing with others, and it seems they should be able to handle that - to take up the slack. So, you should definitely have something that keeps you alive. Might doesn't do that, necessarily, and other players are likely to use that, the other Barbarian, for instance. Holy Freeze would be a boon, slowing every attack from enemies except death lords (frenzytaurs) and reducing the chance of getting hit. When combined with Battle Cry, the only monsters you should be worried about are bosses, and even then everyone can gang up.
As for charms, first thing is resistances. Anything the jewelry can't make up for is paramount. Next, life and breakpoints like hit recovery. It's vital not to get continuously clunked while having no defense, and to at least survive it, if you are. Oh, and defense charms are useless, obviously. =] Mana is good (though not as much, especially if someone's using an Insight), skills are better, etc.