With Nioh, all the weapons were viable and fun - and since each had their own strengths and weaknesses - everything was pretty balanced.
I didn't use the glaive it hatchets in the last chance demo - but I did in both the alpha and beta.
As far as I can tell - the weapons are all, once again, pretty balanced. The only weapon I find harder to use than the others is the hatchets - but again, I didn't use them in the last chance demo. In the alpha/beta, I had trouble using the hatchet's skills against kamaitachi and yatsu-no-kami, being forced to rely on the basic combos only - which made them not as good as the other weapons for me...
But I think this may have just been my inability to get used to them well enough to use them effectively against the quicker bosses. Perhaps they would have been much better had I used more burst counters - which I didn't really use in the first two demos but got more accustomed to in the last chance demo.
So, truly, I think the best and worst weapons really depend on the individual playstyles and they are all pretty balanced.
That said - one thing the last chance demo did show me is that when I get stuck; I need my kusarigama.
The definition of insanity is doing the same thing again and again, while expecting different results. (As defined by Einstein)
Maybe we're all a little crazy.