Here are my thoughts on your build and opening:

1) Your opening is slow, and doesn't have good transition options if your opponent is aggressive.

2) Harmonize on Libro is bad. Use Death Ring instead. It's more efficient, and doesn't setup a strong 2 for 1 for your opponent.

3) If you want to play both the Graveyard and Libro, have a plan for how you're going to defend yourself if your opponent rushes you. If you're generating twice as many resources per round as your opponent, but they kill you on turn 5, you've over-committed to economy.

4) Altar of Skulls takes a LONG time to get going. I would either go for it right away or give up on it entirely.

5) Sardonyx is bad. If you want to play him anyway, include Sacrificial Altar. That way at least you can get some good burst damage out of the deal, and a way to get rid of him if the life drain is getting too painful.

6) I don't think you have enough defensive options. Only 2 cards that give armor, no Brace Yourself, no Agony, no Enfeeble, and no defenses. If you can stay away from your opponent or win damage races anyway, that might be okay, but with your proposed opening I don't see that happening against any aggressive mage. The walls help, but I don't think they're enough.

7) Add Teleport.

Even with 2 creature spawnpoints, you don't need that many creatures. If you drop 4-5 zombies, Malacoda, the Acolytes, and Sardonyx, you would still have a pretty heavy creature compliment, and you would free up 20+ points for other spells.

9) Add a way to prevent healing. Deathlock is probably the best option, since you don't include any healing. This will be huge against the Druid and Priestess, but can be relevant against any mage.

10) How do you plan on dealing with Kralathor?

11) Add some attack spells that will help you against conjurations. Zombies are kind of awful against conjurations, and with the number of creatures you want to churn out, Mordok's Obelisk + Suppression Orb could be annoying. Force Hammer and Hurl Boulder are the most obvious options, but you could use Fireball to simultaneously strengthen you against Kralathor.