I'm finding that Death seems to need to play the outlasting game. Simply wearing people down, making sure fights are in your favour and as one-sided a physically possible. I tend to use Dire Wolves as tiedown units for that reason, while the damage dealers bully and gang on the real threats.
I've really struggled with using Spirit Hosts in this setup though. I run Legion of Blood for the Bravery debuff abilities as those can stack well against some armies. Spirit Hosts I find are that unit which are really good against a particular kind of unit...which is why any opponent that knows you will simply avoid it with that kind of unit. In the same way you keep your monsters away from Big Stabbaz, my opponents simply throw trash units at my Spirit Hosts who don't care about MW and don't care about Rend, which means my Hosts aren't really making themselves felt. They don't really have the speed to outmaneuver things either.
I might consider Hexwraiths soon, though with the Nighthaunt release coming up I reckon I'll wait to see how that shapes up.