Yeah the inscription was just temporary. I usually run exactly with the template you are suggesting. I worked inscription on my Necro-mage to try to make some super slayers. I actually was successful in making a Demon Slayer Spellbook. So my DF problems are solved.
I don't have a -0 mage weapon unfortunately. At least not yet... so I've been using a -15 Staff of Power and using it judiciously. When the higher level spawn shows up I usually go into slayer spellbook or scrappers mode. I use the weapon for level 1 & 2 spawns at the champs.
And BTW, yes I can confirm the 1.5 damage ratio for the Air Elemental book for the DF. When I went to the Demon Slayer my damage went up from the 120 range using a FS on a DF to the 160-170 range per FS. Of course I'm also hitting the DF with corpse skill too.
Anyway... back to making books. I'm going to keep making them until a Repond slayer spellbook pops into my pack!
-OBSIDIAN-