do casualties in the training missions count as real casualties in the final record?

[loreangelicus]

Yup, this is confirmed, patchless and with patch 1.7; Necro Call will not act as a Resurrect for your lost undead troops. As such, you could classify Necro Call as just another summon spell. Same with Necro Call ability of Necromancers.

It's sad, really, since Necro Call is a guaranteed spell (pluck it from the lost book something quest item found in Marshan Swamps), and Dark Commander is a guaranteed support skill (no need to hope for random items that would enhance your army).

You could use Sacrifice and Time Back to "resurrect" undead troops, but even the Sacrifice spell requires you at least have one non-undead unit that can be sacrificed.

All-undead is a viable army, but not for a no-casualties run. Even if you use vampires, ancient vampires, ghosts, and cursed ghosts (units that "self-resurrect") their life-draining abilities are useless against a similar all-undead enemy army. I myself only use one vampire unit even though both are available simply because of this disadvantage.