Personally I don't think the drop off is too bad with the mediums, the race would be better with less wear but it's not a major problem, it's less than 2 seconds slower on lap 6 compared to the start, only that seventh lap is a problem. Of course I'm not a pad user and I can appreciate that there are problems there with this.
Also the people I've seen struggling the most late in stints are all in the Honda, so it's possible that whilst it's quicker over a lap it's not the greatest race car due to the wear, if it indeed does struggle more with this and it's not just the drivers fault or that they all happen to be pad uses.
How much slower is the Hard tyre over a lap? If it's approaching two seconds I just can't see it being a viable option unless you are starting at or very near the back.