Some years ago, I was very much into bladed weapons, collected them (not cheap stainless steel stuff from China, real weapons), read many articles and books, and was part of several online communities that studied swords and other bladed weapons.
As far as effective weapons go, the bat'leth makes no sense whatsoever. Weight distribution, how the shape of the blade would disperse the shock of impact, cutting abilities with the inside curve the way it goes.... Simply does not work as a effective weapon. Sure, it'll kill well enough, but a blunt bar of steel will do that as well if you hit a skull hard enough.
Remember how Dax mentioned that a typical bat'leth weighed about 5.3 kilograms and was about 116cm long?
On average, a Japanese sword would weigh in around 1,2 kilograms, and a average 1 handed 'knightly' sword about the same. I own this sword, a replica of a typica Oakeshott Type XII. Notice the weight and length.
http://www.albion-swords.com/swords/albion/nextgen/sword-medieval-knight-xii.htm
The concept that a bat'leth would weight 5.3 kilos, with what looks like no proper balance, and still be easy to wield, simply does not add up.
Now, before people claim Klingons can wield it because they are stronger, we've seen humans use them as if they weigh nothing, so that doesn't add up.