when it means the kind of boost from soul dew (50% to special attack + special defence on designated pokes) on already powerful pokes (pikachu can't hold it's own if it's life depended on) yes it does. darkrai is already a free kill at least without void. the only stall mon that isn't at least 2 shotted by it at +2 is evostone chancey + even then it's healling too constantly to do anything back is going to prevent a healthy meta which by definition all strategies (balanced, offense (heavy to moderate), + stall (heavy to light)) are viable.Are you sure it would not be broken?
EDIT:
That difference is really not that significant (imo) to differentiate the two. Why does affecting stats mean that something can suddenly be banned? You could say Darkrai becomes insanely powerful with DV with the ability of an essential free kill and free set-up.