Flurry is considered a melee attack for a set such as Viper's Sting, but it never procs the bleed for Dual Wield Twin Blade and Blunt while using an axe. Twin slashes can proc both Viper's and Twin Blade and Blunt's Axe Passive.
While I could sort of see some logic when you earlier said shrouded daggers did proc the bleed (I suppose one could throw an axe ... a stretch for a melee attack, I know ...).
However, if whirling blades will proc the bleed, but not steel tornado, there must be a bug. The bug being that Whirling Blades should NOT proc the bleed, OR that steel tornado SHOULD proc the bleed.
AND ...
If the bug is that steel tornado should be able to proc the bleed, then there is no reason to exclude flurry from the (twin blade and blunt) axe bleed passive (again, if it applies, the axe bleed passive should ONLY have a chance to proc on either flurry's first or last damage tic (but not both)).
Flurry is a channeled melee attack (melee because of the close proximity you are to your target). Twin Slashes, on the other hand, is an 'instant' attack, or a normal melee attack. But, since they are both dual wield weapon abilities, you would think they would both apply the dual wield Twin Blade and Blunt passive.
I can't remember if Steel Tornado triggers the ax bleed while having an ax equipped or not, but if it does, then Flurry should trigger it too (but only on the 1st or last damage tic).
Yea, I know Steel Tornado is an AOE ...
What I'm trying to say is that Steel Tornado and Flurry are not your 'normal' melee types of attacks ... yet both are considered Dual Wield (melee-type) Weapon abilities. So, if one of them procs the Twin Blade and Blunt passive, then BOTH should. However, if NEITHER of them procs the passive, then that would make sense ... in a ZOS sort of way.
This was done on live, so i should do it on the PTS to double check. Steel Tornado, and Blade cloak don't appear to proc Twin Blade and Blunt axe bleed. But, I decided to go and test Shrouded Daggers because why not, might as well say that now 1/5 DW abilities can proc the axe passive, whereas 5/5 abilities can utilize their respective passive for all the other weapon types (I think).
Guess what?
Shrouded Daggers III (A Ranged Ability) can Proc an effect that is stated to only work on melee attacks. I checked this against viper, and viper will not proc off of it. So I don't know what's going on.