A couple things:
Lord D'Tesh doesn't have the Hero promotion. That kind of sucks, since he's the only one they can get and is very late, barring Duin. An early, weaker hero would be nice.
By the time you get him you should have buckets of death (and maybe shadow mana). D'tesh is scary scary.
Graveyards are unremovable - ie if you build a Graveyard over top of a mana node, the only way to get rid of it is to have an enemy plunder it or Worldbuilder it away.
I think that graveyards should be subject to Raise Dead (but not lootable, I think this is being worked on). This would provide extra skellies and remove the "offending" graveyard.
D'Tesh can't build Pastures - quite annoying. Maybe because of the auto-desert convert, but in effect they can't get horses on their own. If that's the intent, should just remove the mounted line...
Try using slaves to build any improvements your regular workers cannot.
As to rest...