I had previously written about the statlist swap bug, but then immediately realized counter thoughts. The statlist swap bug is actually fixed (for anyone that knows what it is). Instead, there’s a different issue. Dual-wielded sequence skills will use the chance to hit (CTH) of the gloves-side (primary) hand for both attacks.
See these YouTube videos I uploaded:
Barbarian
Assassin
Notice how when the 95% CTH weapon is primary, both attack attempts almost always hit with exception of Frenzy (more information about Frenzy later), even the second weapon which only has a 5% CTH (double nova procs almost always). While Whirlwind can’t proc Chance to Casts (CTCs), notice the fire and lightning damage hits. They’re either both rarely there or both almost always there.
Frenzy is an exception, though I don’t know why. Even if the 95% CTH is primary, the second weapon still procs at 5%. This isn’t the statlist swap bug, as you can see I can proc only Frozen Nova (which means the first hit missed and the second hit succeeded, if statlist swap bug were the issue here, we’d be seeing Nova proc on the second hit instead). If you don’t trust the procs, look at the fire and lightning damage instead.
Notice another bug: even though I’m attempting to hit with 100% CTC on Attack (on hit attempt), the CTCs aren’t activating 100% of the time. Sequence skills treat CTC on Attack as CTC on Striking (on hit success).
This means if your primary hand has a high CTH, both weapons have a high CTH. If your primary hand has a low CTH, both weapons have a low CTH.
This bug impacts: Whirlwind, Frenzy (unique symptoms), Double Swing, Double Throw, Dragon Claw, Fists of Fire, Claws of Thunder, Blades of Ice, and very likely Act 5 Mercenary Standard Attack.