stormtide

Do you mean... Bluebie?

What would you suggest I take out?

You have an extra Atraxa, and an extra Vitu-Ghazi, the City-Tree

Start your engines, built to last, and built to smash

This could easily be put in the description instead. Also, I'd suggest gifted aetherborn, maybe yahenni.

Feast of blood?

Oh. Didn't even see that. Sorry

There are some cards that work really well with him since he's the commander
Amoeboid Changeling
Blades of Velis Vel
Shields of Velis Vel
Wings of Velis Vel

Once amonkhet comes out you'll have some more choices. There's an oblivion ring that costs one more but has flash, and an angel that oblivion rings, but has embalm so you can use him (It actually is a him, not her) twice

Is sliver overlord the commander?

I'd suggest long macar, and any other inspired creatures that for in here

I love infect, I love Orzhov, and I've recently gotten into artifacts. +1 from me

Chain Veil?

If you want to splash red, there are some potential cards to choose from. Maybe sideboarded?
www.mtgvault.com/card/lava-burst/ICE/
www.mtgvault.com/card/lava-flow/ME4/
www.mtgvault.com/card/lava-spike/CHK/
www.mtgvault.com/card/scorching-lava/INV/

Athreos? You play cards cheap, then either get them back in your turn or they lose 3 life

You have an extra mark of the vampire

It's 4 or more card types in your graveyard, and you only have 3 card types: land, instant, and creature

You're right. When I looked I forgot to specify standard.

Anguished unmaking, while good, wouldn't work with what I was talking about. I was giving removal that could also get the tree in the graveyard for soul separator.

I don't really see a reason to limit this to vampires specifically. Add in some more vampire tribal
Stensia Banquet
Stensia Masquerade
Vampiric Fury

Since it is in, what's your second choice?