I would have to disagree with you here.
Pouncing with knockdown attribute is one of the best Swordsmen skills for PvP.
But, that’s it.
The rest of Barbarian skills have a very, very slow animation, are clunky and weak. Forget about Warcry and Frenzy as well.
On the other side, Highlander has Bleeding, Wagon Wheel, Crown and Skull Swing.
But still, yes, they face the same problem that most Swordsmen suffer: Close range.
There are currently 2 things that, then, are indispensable to every Swordsman thinking on going to PvP: Cata’s speed and Corsair’s Hook.
Catas are lancers, so they would not be optimal for Highlanders and Barbarians.
But Corsair, on the other hand, offers a ranged disable, that offers you the opportunity to spam a precise combo of skills.
If Barbarian, you would have weak skills, and wasteful stuns (the stuns would be good right about when Hook ends though).
When Highlander would plummet the target’s INT and SPR, eliminate their defense and afflict Bleeding.
This, to me, sums up the question about Barbarian and Highlander on PvP (considering that you pick Corsair for them. If you don’t, then forget about PvP altogether).