Blizzard has announced that at the start of Season 3, bosses will drop tier at a reduced rate (1:3) compared to previous seasons (2:2).
This means that for a Mythic raid, only 1 piece of tier will drop on Season launch (was 2 in previous Seasons). For a 30 player Heroic raid, this means that only 1.5 pieces of tier will drop on Season launch (was 3 in previous Seasons).
The Revival Catalyst will be available during the first week of Season 3.