Horridon
Normal:
There are two parts of the fight that you need to deal with, Adds, and phase 2 burst damage. I highly recommend both Roiling Blood and Blood Tap for this. Roiling Blood makes it easier to keep diseases on all the new adds as they come in. If you need some help getting threat on the adds early, don't be afraid to use glyph of Dancing Rune Weapon. It's a damage loss, but dead dps is a damage loss too. Remorseless Winter works on the adds here, and if you can get the Bloodlords stunned you can help reduce the amount of raid damage going out in the form of the Rending Charge they do.
The reason I recommend Blood Tap is due to his ability Triple Puncture. Try to get at least 1 if not 2 Death Strikes before EVERY puncture. Save cooldowns for higher stacks. consider using glyph of IBF here, though it depends on how long your burn phase lasts. Ill explain that in more detail below in the heroic version to save space.