Everything points to the fact that BRF was intended to be the 6.1 raid.
1) There's NO 6.1 raid
2) All the non-actual raid related items like additional tradeskill, garrison, legendary questline and follower was going in for 6.1 on schedule
3) They had to finish some tuning in the 6.1 PTR
But someone was probably worried about not enough bosses in Highmaul and pressured the raid team in putting it for launch and enabling it "quickly".
I wonder how delayed 6.2 and the third raid is going to be.
Uh
This raid tier is the same as every launch tier since........ Vanilla. Pretty much. TBC had both full tier 4 and tier 5 at the start.
WotLK had Malygos, Sartharion, Full Naxx and Archavon
Cataclysm had Throne of 4 winds, Blackwing Descent, Bastion of Twilight, Pitlord loot pinata
MoP had Mogushan vaults (similar to highmaul) and then Heart of Fear and Terrace of endless springs. Totalling here at 18 bosses (6+6+4+2 world bosses).
They just decided to lag behind with releasing so they can have a bigger gap for the next content patch after 6.1. This makes total sense, look at it from this perspective:
Launch content, 2 months and then new raid opens, then maybe another month and then 6.1 comes. Then you get 3-4 months or so and then we get the next raid tier etc. It makes a lot of sense from a subscription point of view to spread out content. I think they waited a bit too long with BRF though because people started getting bored
ON topic of the raid - I like it a lot so far! We did 4 bosses on heroic for the first night and started working on fifth (oregorger) - Gruul took 2 wipes, Beastlord 2 wipes, Hanz & Franzok 2 wipes and then we had something like 8 or so on Operator Thogar before he bit the dust. Thinking of going for Oregorger, Flamebender and then Kromag tonight, will have to see. Input welcome!
Tank damage is really high in here which means I have to purify a fuckton. Still feel like monk is masterrace though and after we killed operator I was #2 world on tank survivability, which was kinda cool since my gear is a bit lower than those 7/7 mythic raiders