Bottom post of the previous page:
You're not going to be doing 300 per hit or anything. Its not supposed to be the highest damage weapon. A lot of the hh stuff is getting multiple hits in at a time. You should do like 160 or so with the double note on a weak point (total, you need to hit with both parts of the swing)Hitting with a song + encore is like ~250-300 damage depending on how many hits you got in.
You should always have the buffs on, thats like complaining the ig sucks without buffs.
They dont stack, they're both the same song on that particular horn.
If you want more damage do the bone/gama horn or the neirgigante one. Although if you're only in it for big numbers the hh probably isnt the best pick :p