The BT bug had been around forever. You just needed to know the conditions under which it occurred to exploit it. Combining the exploit with RE gaming resulted in very nice synergy and extraordinary throughput.
Conditions ( http://us.battle.net/wow/en/forum/topic/2416208246#4 ):
I'm not going to miss HS. It was effectively a limited version of BB in that its number of targets was restricted, facing was restricted, cast range was restricted, and suffered a higher effective miss rate than BB. In 6.0 when tanks will never miss and damage is not yet set in stone, BB is quite clearly the better choice. With the popularity of Roiling Blood now anyway, BB already currently fills the exact same role as it will in 6.0. There's no point in having two abilities that fulfill the exact same role.There's also a trick you can do to make Blood Tap restore both a blood and an unholy rune as death runes at the same time. To get this result, your runes need to meet both of these conditions: 1) at least 1 blood rune off cooldown and 2) at least 1 F/U pair (1 frost and 1 unholy) that were put on cooldown at the same time (as in, what happens after every time you DS--they both are used at once). How long those two runes have been recharging doesn't matter. You can use Blood Tap to your advantage this way for more Death Strikes or to stop Bone Shield from messing with your rotation. It sounds complicated, but it's really quite simple. If none of that made any sense to you at all, this will work 90% of the time: use Blood Tap when you have at least 1 blood rune off CD.
The final AP coefficient will determine if not scaling with weapon damage is problematic. We don't know that yet.