Only get Ice Blast 1. It’s not that useful, especially not on bosses when ice pike can hit enemies multiple times.
All of elementalist’s spells besides the barrier (from what I’ve heard.) are deployment spells, so rune of ice from RCs won’t work on them. Here’s an example of a build for self-rune casting:
Ice wall’s Psychic Pressure combination was nerfed, allowing bosses to attack players through ice wall, and after ten hits… your ice wall disappears (PP hits ice wall.) The AoE from ice wall shards is only 2-4 characters large, so it won’t hit many monsters.