I'm not quite sure where you are getting some of your point costs from. The Aegis/Quad and the Plaguebearers don't add up to me.
What I would do is:
-Drop flamers, shotgun and autoguns from the cultists.
-Give the Portal to a Herald, and give the
DP the Grimoire instead
-Replace one herald with a Heldrake (should have points left over after nerfing the cultists)
Overall it looks pretty good though, and I don't think you will be getting "Slaughtered" for long

Remember: getting a good understanding of the rules and how to use your army optimally is just as important as a good list.