I made mass threat reduction on playing Doomed for Saruman as a way to offset the inherit disadvantage Doomed mechanic has in multiplayer. Sure, there are fair cards like Deep Knowledge or Legacy of Numenor, they affect all players and it's only right their threat also affects all players. But then, there is "local" stuff like Herald of Anorien, Mirkwood Pioneer, and most importantly - Grima. It is unfair to punish the entire party for the advantage only one player is getting, in case of Grima - 1 resource, which makes him virtually unplayable in multiplayer. That's the flaw of the Doomed mechanic, it cannot target just the right player. So what I did with Saruman's ability is just try to make Grima and non-global Doomed stuff playable in multiplayer.
I even tried to patch this issue up in my "fix the game" pet project long ago: