Lets see what we can do!
Firstly I want to figure out exactly what you want to happen, because I agree with the criticism. it isn't incredibly clear. This is what I think is meant to happen:
1) Hjordis would die.
2) Hjordis gets to move 4 spaces. (This move can not provoke LEAs, because, well she's dead already, so more wounds don't matter. But this needs to be spelled out.)
3) Hjordis begins singing.
4) Opponents figures within 4 of Hjordis are affected by the song and either take wounds (skull), also begin singing (blank/symbol), or nothing happens (shield).
5) for each figure that a blank/symbol is rolled, they begin singing and the process repeats again.
This next part is unclear. We don't know what exactly that entails. Who is affected by the new song of the figure that rolled a blank/symbol)? Is it within 4 of that figure, or within 4 of Hjordis? I think you want it to be the new figure, but the wording doesn't say that.
Assuming my assumptions are correct, Here is what I have come up with.
CIRCLE SINGING DEATH SONG
When Hjordis Muirgen would be destroyed, do not remove her from the battlefield. You may immediately move Hjordis up to 4 spaces, and she never takes any leaving engagement attacks during this move. Hjordis then sings the Circle Singing Death Song. When a figure sings the Circle Singing Death Song, roll 1 Combat Die for each opponent's figure within 4 spaces of the singing figure. If you roll a skull, that figure receives a wound. If you roll a blank or a Valkyrie symbol, that figure sings the Circle Singing Death Song once all dice for the current singing figure have been rolled. When all dice for every figure singing the Circle Singing Death Song have been rolled, remove Hjordis Muirgen from the battlefield.
That's how I would word the power you currently have; however, I would like to make a few suggestions on how to improve the power as a whole.
First, change the name of the power. Circle Singing Death Song is very wordy. Too many modifiers. I'd suggest Spreading Death Song or Spreading Song of Death. "Spreading" describes the song better than "Circle Singing" in my opinion. Second, remove the 4 space movement at the beginning of the power. It seems like a band-aid for poor play. You should strive to position her well before she dies and your opponent should try to kill her in a bad position. Removing the free 4 space move makes her a much more interesting figure to play. Third, add a clause at the end that says " a figure may only be affected by the song once per turn" otherwise this could spiral out of control.
Taking all my suggestions into account the power looks like this.
SPREADING DEATH SONG
When Hjordis Muirgen would be destroyed, do not remove her from the battlefield. Hjordis then sings the Spreading Death Song. When a figure sings the Spreading Death Song, roll 1 Combat Die for each opponent's figure within 4 spaces of the singing figure. If you roll a skull, that figure receives a wound. If you roll a blank or a Valkyrie symbol, that figure sings the Spreading Death Song once all dice for the current singing figure have been rolled. A figure can only be affected by Spreading Death Song once per turn. When all dice for every figure singing the Spreading Death Song have been rolled, remove Hjordis Muirgen from the battlefield.
This was a fun problem to solve. Hope I helped!