So, two days ago I've decided to make free account @NA (as I play on my main @EU), to see if I can climb with Core Necro anywhere, then set my goal to Platinum as Core is pretty kitten compared to Elite Specializations. I reached it within one day of playtime rolling over Scrouges with overall result 14-5 as SoloQ with 150-200 avg ping (played also some Unranked with it, as I had to reach rank 20 to que for Ranked).
Don't get me wrong, it's not about bragging, I just want to share two variants of Terrormancer I've been switching between, because they could be useful for "free to play" Necromancers as it was doing pretty well against Scrouges, due to 1200 range on Life Blast and huge amount of condi transfers and Boon Corrupt turning their stability into Fear, while not being bad against most specs.
Those builds may not be good enough to reach Legendary or tournament play, I believe they should be good enough to have some fun in both Ranked and Unranked.
Spite / Curses / Soul Reaping
Against tankier teams, it's good to swap Spiteful Renewal and Signets of Suffering for Bitter Chill and Spiteful Spirit and picking Consume Conditions over Signet of Vampirism, as additional boon corruption may be needed.
"death by lag - it is your fate
just relax, and meditate"