Simple question: if I have nirnhoned vMA staff on back bar, and when I cast wall of elements on this bar and then weapon swap to front, will I get 15% damage increase from this trait on front bar?
AOE dots will take over the stats of the current bar. Single target dots will retain the stats of the bar they were cast on.
Not all single target DoTs though, Haunting Curse rescales the 2nd explosion for example.
I don't think Haunting Curse works like a true DoT. It's a delayed damage ability like Proximity Detonation. Single target dots are things like Poison Injection or Crippling Grasp which tick damage against one target at a constant rate.