Yea what you mentioned is widely acknowledged but its not an issue, its literally the way its designed. Back in wrath small groups were mad that 10m dropped items of lower ilvl, so they changed in cata so that you get the same gears but to a lower probability of getting them. You have to acknowledge that 10m is just easier overall and it is intended to be inferior in terms of loot, whether items of lower ilvl or less quantity.
So yes, it is intended that you are less likely getting the item you want from 10m than from 25m. Why? cuz if otherwise there will be no 25m groups everyone will be prompted to run 10m.