As usually you can watch those fatboss video-guides or read wowhead guide by yourself. More practical stuff.
I found this video useful because of point of view, group size, group damage they do(our numbers should be close to that) and take.
And overall execution.
It also shows some typical problems with this boss.
a. They miss just one single "Nightmare Ichors" in phase 1(by "miss" I mean didn't kill it close enough to the boss) . So they need to wait for 3rd group of ads to spawn.
b. They pollute area near the boss with "Nightmare Corruption" (purple things on the ground) in phase 2. This area should be as clean as possible all time, besides that part when we gather ads and kill them.
Other then that execution looks ok.
Thing we don't do (well...kind of) on normal but should do on heroic.
1. Actually bring those blood drops to the boss and kill them in predictable manner. DK mass grip plus few stuns will be great.
2. In phase 2 preposition the raid close to "Corruptor Tentacle" spawns (group far right, then far left).
3. Inside boss - that aoe(cursed blood) really do tons of damage. If anyone got hit by 3 "circles" at once - dead. So whole group should be as close to boss as possible.
4. Players targeted by "Spew of Corruption" need extra healers attention.
5. Heroism usage. In this video and few others they use hero at the beginning of p2 to burst down tentacles.