Barb>swash>merc>barb
It's been like this since I started playing this game. And swasies are as deadly as bards. There is no middle ground. 95% of the time they are close to perfection and even op (like grouped bards) or they are complete trash (like most solo bards).
Also who said that 15 hp trains is a great amount of hp? (with 15 you reach a merc's pool at best?) In any case the swashbuckler must not get hit by anything. The hps do not matter. If you are hit you're dead. This is the reason the 95% rule above is true.
And if a furied, hasted, (maybe gsed), large centaur with a vulnerability active weapon and his cabal skill couldn't deal with 700 hp in two rounds then I bet barbs would really suck in a normal situation.
However I agree that most slow/big weapons are not used today. I remember asking about weapons when I had my first character (04-05) and people had always a good word to say about big weapons like great axe (same people of course were laughing at my barb using wakizashi). Then there was the flamberge trend. Pike was always popular. But you had the feeling that slowly, but steadily, favorite pbase weapons are getting smaller and more accurate. From sickle to khopesh to kama to wakizashi to epee. And from pike and trident to bspear. Maybe discussing ways of making big weapons lethal again would be a good idea for a new thread.