Zombies

Well, I don't like ghoulraiser ether. It is a 2/2 creature for three mana (not a good sign) and it relies on your creatures dying to get value. Think for a moment, what else can you do for three mana that gets more value? (hint: dismember)

With a low, aggressive curve like this, you are likely swinging with your dudes as of turn two/three.  If you are applying pressure and doing a lot of trades, like a zombie deck should, then returning a fallen creature keeps you on the offensive.

The only three drop zombies in currently in Standard are:

Cemetery Reaper (already there)
Contagious Nim (not using poison)
Ghoulraiser (already there)
Glissa, the Traitor (off color)
Phyrexian Crusader (good card, but again, not using poison)
Unbreathing Horde (already there)
Warpath Ghoul (same cost, one more power, not other abilities)

If I were playing standard Zombies, I'd go Black Weenie style.  If you hit:
T1: Swamp, Diregraf Ghoul
T2: Swamp, Walking Corpse
T3: Swamp, Cemetary Reaper

By turn three you've got 8 damage on the table! 

Oh, and yes Dismember is very high for power-level.  It wouldn't be a bad idea to add some, but don't loose the creatures.

As you can see the three-drop slot is really covered. Also, what are the chances that a zombie will die when you cast the Ghoulraiser? Just put in the Skinrenders.

Sorry, looking at your current list, your creature curve isn't that aggressive anymore.

I think four Call to the Graves is a little high as well.  It's worth having, but you don't want two in your opening hand either.

Keep the ghoulraisers and remove two of the call to the grave's. Four is way too many. I do however agree on keeping the ghoulraiser because the whole point of this deck is to have an army of zombies on the battlefield. If you have endless ranks of the dead OTB and then you play a ghoulraiser you are adding a zombie to your hand and one to the battlefield which in turn will allow your endless ranks of the dead to start producing more zombie tokens. It is also useful when your cemetery reaper gets destroyed by something like a fireball which will reduce your zombies power/toughness. ghoulraiser IMO is a very useful card. Also check into nim deathmantle puhhhhlease. I really truly think it is a very underrated card. I have started using it and I have been so impressed with it. It is a gamechanger.