Manastorm Mechanic Questions

In 3.9 we will have this shield.

https://pathofexile.gamepedia.com/Manastorm
But it need some clarification.

1. Will it have separate stacking buffs for each spell casted or only one with higher value will work? Or shield effect cannot be triggered more often then 4 seconds?
2. In ExileCon Chris said, that trigger will occur only of full mana https://youtu.be/tVdpOCxRwj4?t=17010. But wording on shield dont have this information.

This things is very confusing and you can't plan your build in this state.

He does not explicitly state that you would have to have a full mana pool. I believe he is just referring to having a full mana pool as making the most ouf of that mod.

The way he words it could suggest that subsequent casts will increase the damage further, but it might also mean that only another cast at a full mana pool will result in actually keep your damage that high because it does not stack.

We will have to find out when we get it, and I would not plan a league starter around it.