I keep trying to make a list with LoS too and find myself running into a similar problem. Mostly asking what else I could spend those 310 pts (for the battalion and engine) on, and how many spells I really need.
Way I figure, I want Dread, Vigor, Danse, and Curse of Years every turn. Maybe a 9" Soul Harvest through a spell portal cause that's just darn fun. That's 2-3 necros and Arkhan. Throw in some endless spells and I'm good, why invest in the battalion? Sure, more spells, an artefact and a cp, but for the same exact pts you could take 1 more necro, prismatic palisade, spell portal, cogs and 1 CP.