Interesting things on the PTR
Obviously this could change before going live, but at the moment gear ilvl increases as you get deeper into the raid. The first few bosses on normal are 690, increasing to 695 and 700 as you get farther in. Ditto Heroic and mythic, but starting at 705 and 720 respectively.
Set gear stays at the median level throughout, 695.
Might mean it's worthwhile to keep running Normal mode longer, clearing as far as we can on each difficulty for a while. Especially for weapons that might not be available in a specific "type" in the first few heroic bosses.
Blue comment about it, it's officially the new loot design for 6.2. The deeper in you go the better the loot gets, meaning last few bosses in normal will be competitive with first few in heroic. Will be some interesting dynamics depending on what items drop where.