Damn I'm glad I play under comp, Not getting a LOS from Dwellers would be terrible! Regarding Life magic, the main problem I remember having was that you had to roll exactly the right spells in order for it to really kick off , which isn't easy with a lv.4. Flesh to stone is great, so is regrowth, but not so much if you don't roll throne of vines. Dwellers is awesome, but if you don't have the 2+ ignore miscasts it's really risky. Or sometimes you roll something like Throne, shield of thorns, awakening of the woods, and regrowth.
Shadow has a majority of excellent spells, which aren't interdependant, but also have great synergy.
I don't think you can simply say that x lore is best for empire because y, it depends on your army build and playstyle. I'm personally digging Light magic for my mostly mounted empire army, the buffs are really good and make sure my units can reliably hit and kill things (WS I 10, ASF +1 A), as well as survive (-1 to hit, Net).
Just my 2 cents,