You are right! It does say unmodified armor save (even though some equipment modify the original armor save, but it clears it up with the example of a heavily armored knight riding on a barded horse being 2+)
So.. Lore of Metal? still viable! Too bad that Asaph archers don't benefit from Enchanted Blades, but Grave Guard does! Skellies can benefit from Glittering Robe. Transmutation of Lead is the worst we can use. Also, casting Plague of Rust on a Daemon Prince several times (1-3) makes him very vulnerable to ghoul/crypt Horror's attacks.
Warriors of Chaos < Terrorgheist
That's the truth of it, although infernal cannons can cause some damage. Yep, apply a V. Lord or flank them with cavalry of your own. It doesn't matter if they have ensorcelled weapons or not... the beasts themselves are Daemonic, and have magical attacks (and hit very very hard).
Fell Bats and Dire Wolves can keep those dudes busy all day and away from the battle until you can destroy them.
This is the very example of "we don't win by overpowering, we win by cunning" that our army has to offer.