Taiji

The combination of the ice spear with the freezing effect doesn't significantly outperform the combination of burning with the fire passive in terms of damage. However, it is more time-consuming and expensive in terms of gems. Furthermore, ice lacks area-of-effect (AoE) skills. Yes, you can replace the flame with a cloud, but it's more expensive and riskier for the team. Also, if the character is a succubus, the flame can be centered on herself, but the cloud shouldn't be.