Double curse with hexblast spell echo bug?

I have Whisper of Doom which gives me to apply 2 curses to the enemies so I added spell echo to the hexblast spell but it doesn't add a second blast to trigger the second curse. Maybe it's not supposed to work I'm trying to understand if that's the supposed outcome that hesblast can't echo.

Edit: even spell cascade doesn’t work with hexblast.

Hmm, i was about to respec into this but i'm about 50k short on gold to afford it, following the thread for later.