The Water Elemental is not made for attack, it is made to distract enemies and take their attention off of you.
That is why it consistently heals and shields itself while taunting the enemies. For storm, this is very helpful in the lower levels when you have lower health (believe me, I know) since the Water Elemental can allow you time to blade, trap, and do whatever else you need to before attacking a boss.
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Bladed Seraph