It seems that injuries would take a long time to heal due to the effect of the curse shield.
That is very dangerous.
There is no clear distinction between friend and foe. In addition, there is a counter effect on allies.
I must not even think about using it.
Also, after looking at the shield tree, the unsealing wasn't progressing at all. It was only for a short time, but I know I cannot unseal that shield. I somewhat remember having that sort of hunch.