From the
April-30-2013-(JST)-Version-Update notes
"The job trait Desperate Blows may now be learned at level fifteen*.
Desperate Blows reduces delay for two-handed weapons when using Last Resort."
Meaning, unless you were using a great sword, you weren't getting any delay reduction via last resort.
It doesn't. You must have a weapon equipped in both the main and sub slot for dual wield to have any effect.
This becomes extremely clear when you single wield /nin, and still have your original tp per hit.