Bear Warrior:
Instead of Standard Rage or Whirlwind Frenzy, you get the
Bear Polymorph Rage. The good thing about Bear Warrior is that you can get +12 strength prior to reaching level 20. Basically, you are very tanky, very strong, but in my opinion the Standard Rage and Whirlwind Frenzy builds become the better paths around level 25+.
Anyhow, the Barbarian 20/Bear Warrior 10 basically gets more uses of rage and that one extra feat at level 20. One could argue that you would be better off going for a Barbarian 8/Bear Warrior 10/Fighter 12 build. The weapon focus/specialization unarmed feats should work both in and out of your bear shape - but since you only have 5 uses of Rage with the Extra Rage amulet - you will want to get Extend Rage V feat to get as long rage duration use as possible.
Weapon Master:
Weapon Master requires six feats and at least 13 in both dexterity and intelligence. The feats you need are: Dodge, Mobility, Spring Attack, Combat Expertise, Whirlwind Attack, and Weapon Focus.
Thus if you go for a human Barbarian 22/Weapon Master 8 - you will have three pre-epic feats to spend on something else. The human bonus feat, the barbarian bonus feat at level 10, and one regular feat left over from the PRC requirements. Basically, you have just enough feats to pick up the Ice-Troll Berserker and Improved Power Attack. (Improved Power Attack is taken at level 18.)
Now, since you can purchase epic +4 weapons on the server, you can can pick your preferred weapon from the list of: Warmace, Greatsword, Longsword, Scimitar, or etc. Personally I would lean towards the Warmace because it comes with the Keen Property and how it tends to be the cheapest weapon - but since it is a two-handed weapon and because you lack the Tower Shield proficiency - I would go for the Whirlwind Frenzy for the extra Dodge AC it provides. But regardless of the choice of weapon, you can pick the
Thundering Rage feat and deal some extra damage on those critical hits. I would go for as high strength as possible to boost the damage and AB. (Trolls are good experience, but you will need to use a weapon that has Acid or Fire damage on it, which does make the scimitar look like a pretty solid option.)
The downside of the above build is its low saves and the lack of Steadfast Determination. Meaning, a unlucky roll of a 1 is enough to fugue you. It will happen once here and there against mob casters that throw save or die spells, but it is not that big of a game-breaking issue.
You can get a lot out of the amulet that provides you with free Extra and Extend Rage feats. But with whilrwind frenzy your rage duration is relatively short. But then again, you do have that critical hit probability on your side. And if you pick a one handed weapon, you can go for standard rage and use a heavy shield for some extra AC.
Additionally, while Northlander Hewing does not increase your critical hit damage output, and it decreases critical hit probability by lowering your number of attacks, it can free you a feat for something else.
Edit: Generally speaking, Barbarian 20/'Something Else' 10 builds work just fine. It really boils down into what you want to play as. Even that Barbarian 20/Duelist 10 works and surprisingly well with any melee piercing weapon.
But if you want to have the best Barbarian Build possible:
Barbarian 20/Divine Champion 10
Barbarian 20/Warrior of Darkness-Anointed Knight 10
Barbarian 21/Fighter 4/Battlerager 5
Barbarian 20/Fighter 10
(In no specific order, what someone thinks is the best build depends on their preference.)