For me the big problem with Dark Frontier is they didn't justify the Borg queen specifically wanting to grab Seven. Her motives there seemed kind of arbitrarily and did not make sense in the vein of everything we know about the Borg. And it also didn't make sense that the Borg would go about getting what they want by extortion.
Definitely the 'Nerfing point' of the Borg in the Voyager series.
Fair point, that did bug me when the offer was made, or Seven was told she wasn't being re-assimilated. It just didn't make a whole lot of sense that bit.