I played against a bent slaanesh summoning list last night for practice. I killed everything I could (two keepers, exalted chariot, 30 daemonettes, 5 hellstriders) and he had 70 depravity and summoned two new keepers and 10 daemonettes back, then piled in twice with each keeper to wipe my brutes and megaboss. I played my best positioning wise with good charges to overload each hero to make sure I'd always have at least one unit swinging first to go for smash and bash.
Things that could have gone different:
1 - I was not -1 to hit for the first battleround. I may have had some extra ardboyz on his back objective for an additional turn to buy me another round of scoring.
2 - I did not get any command points back. I maxed out at +3 attacks only for my first waaagh. If I had maybe got to +7 I think I could have killed all the heroes in the first swing.
But, he was just proxying the army, and I think a good player will always keep one hero safely away wrapped with chaff.
Maybe you need the double to take all the heroes off? I feel okay about the matchup but it's still difficult.