90% of "instant death" is still "instant death". 90% of "way too much hitpoints" is still "a ton of hitpoints" and 90% of "don't stand in Spouts you moron" is still a dead raider. Same Death Blossom and multiple Penetrating Bolts hits. And throwing ball like crazy.
Sure, boss will be dead before the really dangerous waves of adds start, but it's still a long way to get there.
You will still have to do the fight the same way, however if you were doing it before and had the mechanics down, it should be much easier now. Dread thrash damage down, add aoe damage down, platform add hp and damage down, hp on phase 2 adds down. All points to a much shorter and less random fight. Not to mention the 5-6 ilvl increase on the raid.
zerging implies you can ignore all mechanics and just burn boss. you still have to do every mechanic pre-nerf. the only difference with this nerf is that it will be easier to heal, and it wont take as long.
If you see the faint grey circle on your minimap of the Dread Expanse, the "center" for purpose of add grouping is slightly N-NW of the center of the circle. Hunters from guilds before salute you in your attempt to group up adds. The easiest way is for your hunters to have Track Elementals, and give them assist to throw down a world marker. They should be able to roughly adjust it each wave til perfect, then it's there for the rest of the night.
And if you're talking 25 man for breaking huddles, just stop breaking huddles at all after the 5th wave (last wave of 3 adds). Even if they're on healers. You should have enough healers and offhealers to get you through huddles in the offcase that 3+ healers get huddled. In 10 man, always break huddles, since you're only using 2 healers.