Melting Maelstrom not doing any damage to enemies

The Melting Maelstrom mana flask is doing zero damage to enemies. It says:

"

Every 3 seconds during Effect, deal 100% of Mana spent in those seconds as Chaos Damage to Enemies within 3 metres
Deals 25% of current Mana as Chaos Damage to you when Effect ends

It didn't seem like it was doing anything while I was playing, so I went and tested it in isolation and yea, its not doing any damage. It does the damage to the player when the effect is over, but it doesn't do damage to enemies no matter how much mana I spend during the effect.

I tested it on more than one character, with more than one spell.