What is this I dont even...........
At least compare the right things.
Look at the gear you have to use for a 5 hit, then look at the gear for the almost optimal 6 hit.
5 hit:
http://www.ffxiah.com/item-sets/205808
6 hit:
http://www.ffxiah.com/item-sets/218925
To use the 5 hit you give up 9% DA, 3% critical hit rate, 22 STR, 15 DEX, 59 attack, 6 accuracy, 1% haste, and what you really gain is WSing every 10.5 seconds after making 5 attacks, instead of WSing every 12 seconds with 6 attacks. (or something to that effect, I forget the exact numbers and I cant seem to find where I wrote them down) The point is that you only gain about 17% damage moving from a 6 hit to a 5 hit, when you don't give up anything else, and you give up tons with Ukon to do it, so you're really only gaining about 8-9% damage like you said (in comparison to the old 6 hit). The problem is that everything you give up from the new 6 hit totals much more then an 8% damage increase. The DA and Crit rate alone that you're giving up total more then 8% damage, and then there's a bunch more extra stuff!
EDIT:::::::::::
This is also assuming you don't have to use Carbonara for the 5 hit, which I think you do, which is an increased loss of an extra 3 STR and 87 attack!
This also doesn't even cover the most important fact, with the 6 hit, you get to use armadaberk, which is nice to look at, unlike WAR AF3 body!