Oh yea I knew it said "melee attacks" somewhere.
It says it in the actual set bonus description, which you can only view if you actually have the set bonus active. A lot of these are very different from the actual item descriptions so I should try to include more. You can also see the set bonus icon here using the same icon as the "slicing blow" feat, which is a bit of a hint that it is indeed bleed damage.
Set bonus Description:
Also went ahead and tested it again to make sure nothings change and confirm numbers... Was some arguement saying it dioes a minimum of 3 damage, but I got it to only do 2 again - took me hundreds of swings, it's very rare for some reason:
And here's a pic of the duration since they added that to the tooltips:
Shows 9 seconds, so it's 10 seconds:
1 Initial hit +
1 hit at 8 seconds
1 hit at 6 seconds
1 hit at 4 seconds
1 hit at 2 seconds
nothing at 0
Will add some pics to op.