I just happen to notice that using Sprint with Dualcast on automatically cancels the buff (was doing unsync dungeon and I decided to sprint to next set of mobs to use my dualcast and it removed it).
After that I decided to test it on purpose to make sure I wasn't mistaking something and confirmed it does cancel it.
Seems odd it should cancel it so I was wondering if there is a reason why using Sprint removes the Dualcast buff.