Spell speed isn't bad, there just isn't a situation where you can increase it without sacrificing Determination, Critical Hit Rate, or Accuracy. There may be a rare circumstance where you are capped in accuracy and have a toss up between Piety and Spell speed, and that's the only case where it might be better to have spell speed.

Without Spell speed bonuses, Selene would be only half as useful, and so speed does play a role.