…The original poster did say they wanted to deal strictly fire/cold/lightning damage…
While it isn’t entirely pure in that regard, I’d recommend building a Sky Shard/Rune of Hagarrad Mage Hunter (Arcanist+Inquisitor; and in any case, the piercing is part of the flavor of the razor-sharp ice). You’ll need AoM for that, though.
I’m playing a Vitality/Chaos warlock and has been nice
Arcanist compliments every other mastery really, arcanists based classes are the most balanced and “nicer to drive” classes really, at least for me. Quality of life you get from having mirror + extremely strong CC resist pack in form of conversion, plus tonns of spirit to equip rings/amulets + OA + nullification + casting speed. Man. It feels so good in Crucible when you have mirror and nullification, much more control with it. Arcanist mastery is nuts 
Yeah. People hating on s&b for being a no-brainer boring safe playstyle. They forgot arcanist. Difference is arcanist isn’t boring.