Orb of Imposition needed to be weakened, but this is too weak. It should have let you impose the penalty to one saving throw, after it was rolled, as a free action.
Wouldn't that bring back the issues of lockdown, to some extent? After all, if you have a narrow window of saves (by stacking penalties) then a critter needs to get lucky twice in a sequence of rolls if the power is applied after the roll is made (and it could be the case that the first roll is unbeatable guarenteeing one round).
Now to get the huge save penalties of the OoI you have to actually use the resource . . .
I'd agree with you if there were very options to generate save penalties but the list seems more extensive over time.