Hi support team,
I have experienced an inconsistent behaviour with maelstrom stacks, at least judging by the wording on the tooltip.
Swirling maelstrom states: “You have additional Endurance Threshold per stack of Maelstrom.”
but, when I have “Storm’s Aid” which allows me to cast maelstrom on my minions, those casted on minions are not counted as “my” maelstrom stacks therefore they do not give endurance threshold from the 4 point bonus of Swirling maelstrom.
If it is intentional I’d expect the passive to state that it gives a bonus per maelstrom stack ON YOU specifically, because currently it is confusing.
My expectation was that maelstrom cast on other targets would also give this benefit, as they still show up on my buff bar as normal maelstrom stacks. Also when I paired “Storm’s Aid” with “Violent Squall”, the limit of one maelstrom stack did not apply per target, meaning if I cast maelstrom on a second minion, the one on the first one disappeared. This to me is perfectly clear because it does not state that the one stack limit is per target, but it reads as: “YOU can have only one maximum stack of Maelstrom.”
In this case I would expect it to be the same the other way around so that I can benefit from the stacks casted on other targets regarding the “Swirling Maelstrom” passive point, if those on my minions are treated as MY stacks for the above mentioned skill point.
This means I do not get the upside of one option but get the downside of the other, leaving me with only a small amount of endurance threshold for those stacks only that I have on my own character if I want to be able to cast Maelstrom on multiple minions.
Screenshots:
Without any Maelstrom, Endurance threshold = 205
https://imgur.com/VKH03GA
4 stacks of Maelstrom on self, Endurance threshold = 285 (4*20 correctly applied)
https://imgur.com/a/t0Z1pvy
4 stacks of Maelstrom on a totem minion, Endurance threshold = 205 (no bonus applied)
https://imgur.com/a/sn0khVn
If my expectations are wrong then I think a clarification in the tooltips would be benefical for these two options. 
Cheers,
BiggyZable