I'm guessing the bloodlust change is so that when groups with 1 shaman wipe the cooldown will be up 5 minutes faster than before. It might also be to stop forcing groups to have 2 shamans for maximum bloodlust uptime. This is a buff to 1-shaman groups, and a nerf to those with more.

For the most part, if you're getting to raid bosses within 10 minutes of each other you don't need bloodlust. Having a BL at the end of one boss and the start of the next could cause this to be a problem, which realistically could happen for patch > grobbulous. Also Grobbulous > Gluth is another culprit due to having no trash in between. Sapphiron and Kel'Thuzad are both longer than 5 minutes and now don't benefit from having a second shaman, but are exactly the same as with one. Even though ending Saph with a bl would mean it's not up for the start of KT, but you want to save it for KT phase 3 anyway. There's no reason to end Saph with BL, but it could happen on an 11 minute kill.

There are a few times where it could hurt in 5-mans, but how many 5-mans are run with more than 1 shaman, and how many of those wouldn't dominate without the extra bl? Worst case it causes you one wipe on each boss, and if you're really afraid of wiping, just die to get rid of sated and reincarnate.

For overgeared groups(ie wiping isn't an issue) with two bosses next to each other, I don't see how it's worth the time to die+res.