"hardly reduced" is correct and usable in written English.
You can use it to describe something that has been minimally reduced or diminished. For example: The workload increased drastically, and my stress levels hardly reduced.
A single question is used to measure self-reported work ability: "To what degree is your ability to perform your ordinary work reduced today?", with the following response alternatives: hardly reduced at all, not much reduced, moderately reduced, much reduced and very much reduced (score range 0 4) [ 41].
The stricter requirements have hardly reduced the numbers in the long term.
My sense of trepidation was hardly reduced by watching Arsenal play Locomotiv Moscow in a bar opposite the hotel.
The centrepiece of the old approach was a "cap-and-trade" scheme, festooned with offsets and bribes – bribes that purportedly, but hardly, reduced carbon emissions.
No, said kendoken, it is going to get a lot worse: "This 'spike' in oil is purely speculative, the global demand has hardly reduced at all over this sorry episode.
However, the crystallinity of PHBV was hardly reduced.
That, he said, would hardly reduce enrollment and would create a larger nest egg for retirement.
Al Qaeda, F.B.I. agents reasoned, would hardly reduce the death toll with an alert that might have saved lives.
Mr. Malamud said that the volunteer work hardly reduces the need for the government to increase its own digitization efforts.
A negotiating process that started eighteen months ago with talk of trillions of dollars in deficit reduction ended in an agreement that will hardly reduce the deficit at all.
Unfunctionalized MWCNTs hardly reduce the viscosity of PMII.
