The super uber dupers will use BOTD and beast, but I suppose you are far from getting those items. Good choices are BK set, DCs, Djinn Slayers, LS, Azures, Horizon's Tornadoes, Stormlashes. Dual wielding is much better, but if you preffer 2 handed there are acceptable options like Windhammer or Ethereal Edge.
Range is something welcome for WW, thus you may look for good 3+ range weapons. The one handed or swords (1/2 handed) weapons must reach -35 speed and 2 handed ones must reach -60 speed. Dual wielding characters will swing once each 2 frames, 2 handed or single handed will swing once each 4 frames, that is, twice as slow. As for classic, it's 1/1 in 1.10, that is, twice as fast as in 1.09. You must check base speed and the ias the weapon has. Weapons like war pikes, thunder mauls and legendary mallets are quite slow, and it's very unlikely that you will get any that can reach the needed speed unless with very low damage.
Shields can help you survive by blocking, resistances and some damage reduction, but they will reduce your killing power greatly. I don't see many reasons for using a shield for PvM. Barbarians are already weak, you don't wanna WW twice as slower still.
As for uniques, the best option are DCs: 66% deadly strike, good ias (no shaels or ias jewels needed) and good ed. Azures and Stormlashes are also quite good. My barbarians uses a DC and a cruel/eviscertion and does quite well*.
*cookie-cutter builds like blizzard sorcs, hammerdins, trapsins or javazons will always kill monsters much faster than any melee character, of course. Even the BOTD/Beast would look like a merc with no weapon near them.
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