+1000 I second this!
I raid 10m and it seems the past few weeks all we've been doing is DE'ing leather/agility gear that no one needs. Only seen a couple thunderforged pieces drop and I've gotten zero upgrades (still stuck on 525ilvl) this past month.
I've watched livestreams of 25m guilds raiding and the thunderforged gear drop rate is ridiculous compared to 10m. Faster gearing for 25ms = faster progression as well.