Dragon Tail carries with it an attack speed penalty
of 40. This is equivalent to 40 EIAS. Dragon Tail has the worst
frames/attack ratio of any of the assassins attacks. It's one of the
prices you pay for the rather high damage numbers this skill is
capable of producing. Other than the base being different, Dtail uses
the exact same animation as Dtalon. Just as with Dtalon, the
animation has the same AnimationSpeed and DrawnFrames regardless of
what weapon type you use.
Here are the parameters for Dragon
Tail:
AnimationSpeed = 256
DrawnFrames = 13
Base = 100
Penalty = 40
You can find EIAS and BoS/IAS tables
for Dragon Tail here. 7 fpa is
the fastest this attack will go with any weapon.