Betrayal at House on the Hill - "Voodoo" (Haunt 25) - Do you continue if the traitor dies?
You should continue.

The rules for winning and losing are defined by the specific scenarios, not the general game rules. The (heroes) rules for haunt #25 state what is required for the heroes to win:


  You Win When ...
  ... you destroy all of the dolls and at least half
  (rounding up) of the original heroes are still
  alive. 


The main rulebook does NOT say that you must have a monster in order to continue with the traitor dead. What it says is:


  The first side (traitor or heroes) that completes its goals
  for the haunt wins the game.
  At least one hero must survive in order for the heroes to win.
  However, some haunts include goals that are written so that
  the traitor can still win the game after he or she dies. For
  instance, the monsters that player controls may be able to
  win the game without the traitor’s help.


(Emphasis mine). The idea of having monsters to help you win is just one example of how the traitor can win after he dies. It is clear that in order for the heroes to win, they need to meet the requirements in their rules. Killing the traitor has no effect on this (unless their rules state that specifically).