Worse is Doomsayer's Proclamation, which makes nearby enemies roll twice and take the worse result when they're saving against fear effects... which would be fine except that the warlock only has ONE fear power that has save-ends, and it's the level 1 Daily "Dread Star", which you're probably replacing at 15th level anyway. It's not even good for boosting allies' powers, because there's only three save-ends fear effects in the book: Dread Star, Astral Whirlwind (the Astral Weapon paladin paragon path's 20th level power), and Prismatic Spray (lvl 25 daily wizard attack). Sad.