Just to start this discussion, Barbs purely have the advantage over all types of melee players.
Paladins have a good start with multiple hits from zeal, as with druids. But both of them lack major damage properties.
Concentrate has both damage and AR along with the invincible property of un-interruptiblity.
Also barbarians have Berzerk. Zerk is pure magical damage meaning it wont take many hits to kill an opponent.
The problem with zerk is that it takes ur def to 0. this problem can be solved though. Use combos of conc/zerk and you wont get locked as badly and if u manage to land a zerk, the duel may be over.
Assassins seem like the ultimate duelers. But really they mostly rely on the stupid FoF bug. Barbarians can use berzerk on them anyway. Mine usually 1-2 hits asns. depends on their health quantaties.
Barbarians have masterys. another good principle of their build. Use what wepon you want and get extra damage for it. Get iron skin up a litte, or shout then your defence boots to levels where non-eth users are screwed.
Ill post more to talk about later. i got stuff to do. leave some comments peeps. ill answer questions if needed.