Nifft
Penguin Herder
Well, let me say this: it depends on the composition of the monsters you fight.From an optimization perspective, it is tough to beat (and maybe impossible for a Warlock to beat!).
If you are in a fight against a Solo, it's totally useless.
If you're in a fight against two Soldiers and a Skirmisher, it's nearly useless.
The Rod of Corruption really shines when you have a Controller screened by Minions. (Actually almost any encounter with Minions brings its luster to the fore.)
Cheers, -- N