Hey OP, I don't have much to add, but I think I should mention this stuff looks awesome, and I love the BG on this chapter.
First: the shit about them being good at melee and ranged. Ignore the faggots saying that doesn't make sense. Fluff says that they drill all of their combat skills like there's no tomorrow, and their natural talent is immense, added onto their technological advantages and such.
Also, them falling to Slaanesh whilst fighting corn makes sense, don't listen to the guys saying it's derp, because half (not literally) the imperium falls against chaos that way and.
Oh yeah, the one thing I don't like is the warcry, it's kinda cheesy. Also, I'd go a bit further into the blood drinking/mutations thing. Maybe some more into the vampire thing? Slaanesh is vain and cultured, just like the blood angels, and vampires, I think you've got a perfect combo here, keep on trucking!