I'm not 100% sure what the cause is, but from kills the 4x surge only works for a minute or so when you first get your super, but eventually stops giving the 4x surge. Also the 4x surge off of sustained damage has not worked for me a single time, but the super gain off of sustained damage does. I can't confirm, but I think the sustained damage rework is what interrupts the 4x surge from working? Once it's fixed, I am excited to use it with 4 piece Iron Battalion with all Powerhouse armor to be the Song of Flame champion ;)