Chill (detonating Pestinental Blast) scales very well with base spell damage increases. Death Channel can be useful there, although personally, I still prefer Death God.

I do not agree with using Parasitic Soul Swarm, at least when using Death God. The occasional instant Ice Strike imho doesn't outweigh the massively higher crit damage you do with Ice Strike. Also, Ice Strike gets better buffs by Spellweaving.

I just tested what it does to include Parasitic Soul Swarm in my usual spellcasting routine on a Strawman, and DPS went from about 1300 DPS to about 1100 DPS (T4 armor/ring/necklace/cloak, T3 demo weapons, Chilling Breath, not using spellweave).