I'm getting confused by all the ways you can get tier PvE gear. Here's the list: in all cases 10 man raids give T7, 25 man raids give T7.5.
Helmets: T7, T7.5
Drops in Naxxramas from Kel'Thuzad
Shoulders: T7, T7.5
Drops in Naxxramas from Loatheb and from Gluth
T7.5 purchasable for 60 Emblems of Valour
Chest: T7, T7.5
Drops in Naxxramas from Gluth and from the Four Horsemen
Drops in Archavon
T7 purchasable for 80 Emblems of Heroism
Gloves: T7, T7.5
Drops in Obsidian Sanctum
Drops in Archavon
T7 purchasable for 60 Emblems of Heroism
Legs: T7, T7.5
Drops in Naxxramas from Gluth and from Thaddius
Drops in Archavon
T7.5 purchasable for 75 Emblems of Valor
The helmet's clearly the rare item. Kel'Thuzad is at the end of a long instance and is a fairly challenging fight. Everything else is relatively easy to come by if you're in Naxx frequently except for the gloves, which only drop in Obsidian Sanctum and only one a week if you do the boss the easy way.
I think it's interesting that they've decided to let you use badges to buy most of the tier gear. It makes a lot of sense, one wonders why they never did that in BC.