And now on topic, there is 2 main objectives you need to accomplish to crumble his army:
Kill Harbringer and debuff blightkings.
To kill Harbringer you can use fighty flying units like Morghast, that would be a one-way trip for them, but it's well worth it. Or you can kill him with spells, like 8 arcane bolts from Nagash, Curse of the years from Arkhan, Amaranthine Orb through Spellportal.
To debuff blightkings all you really need to do is cast Overwhelming Dread and they no longer get exploding attacks or blades of putrifaction. On top of that - add geminids to render them completely useless, they can also help killing Harbringer.
With those 2 done you can proceed to destroying his army - a Purple Sun can be a great addition to your roster since it doesn't care about any of their defensive abilities. And just destroy everything with 40 skelletons buffed with Dance Makabre.
To hinder his advance whille you try to kill HoD - bring dire wolves, they work as a perfect screening units.
Also being a Death player you shouldn't have a problem with MWs sniping your characters, Nagash and Mortarchs have a lot of wounds as does VLoZD which can heal d6, Necromancer can simply shrug wounds to chaff. The only support pieces that can be in danger are Corpse Carts, VLs on foot and Wight Kings and you don't really need them to build a good list.
Is there anything else that troubles you about his list?