Random spells generally favor the caster. Sample size has to be fairly large to draw any real conclusions so brief trends are irrelevant. I haven't seen anything yet that indicates there's any selective process in play. Most of the time the spells are irrelevant or in my favor. But last night I lost my first rebuild turn after playing Reno to him casting Forbidden Words.
I am willing to admit that I love this card even with the hero power.