Platform: Windows
ISP: Comcast
Type of Internet Connection: CATV
Internet Connection Speed: 15Mbps
Date & Time: Sept. 23, 2018 12:00AM EST
Frequency: Reproducible
Character Name: Galaga
Race: HumeF
World: Carbuncle
Main Job: Red Mage, Lv.99 (Master)
Support Job: Scholar
Area and Coordinates: Any Zone
Party or Solo: Party with multiple members and trusts
NPC Name: None
Monster Name: None

When casting Haste or Haste II on a another party member using the Duelist's Torque (at Rank 12) equipped, the duration of the effect did not increase.
I attempted to cast the spell both on other players and trusts within the party.
I only equipped a single piece of gear and tested while wearing no neck item and then while wearing the Duelist's Torque (at Rank 12).
The effect Haste only lasted 3 minutes in either case.