Not sure if I’m missing something, but as soon as I put a point into the Focal Blast Node (the one that turns it into a line instead of single target) it doesn’t seem to be able to freeze anymore.
I’ve added and removed the point in that node twice now to make sure, and it either is reducing, or entirely removing the freeze rate on Lightning Blast.
I freeze mook level enemies fairly regularly without the node, and with the node I have not once been able to freeze anything across hundreds of casts.