Maelstrom should be applying chill constantly to enemies, but testing this on the dummy (and the enemy dummy) it only applies stacks of chill once when an enemy first enters the effect (either by casting it next to them, or walking into the enemy with maelstrom active). Then after 4 seconds the chill wears off, even though I have many stacks of Maelstrom with an almost 10 second duration.
Only by recasting maelstrom will more chills be applied, and even then it’s rolled per stack cast, so at best 1 chill per cast, again it ignores the maelstrom stacks I have active.