That seems to be the consensus is that you have to micro hard as hell to play Slaanesh without some form of other chaos reinforcement. At the least the campaign will allow you to recruit allied troops where you have an outpost (If Chaos can do that, I believe they can). Hell just getting some basic Chaos Warriors or something akin to Mirror Guard would help a lot.
The Dark Prince being the 'Skate Fast, Eat Ass' faction is sensible but I think if you want a decent time of it you either need to get those allied troops or just play Chaos Legion so you can bring in some heavier soldiers. As for their lack of range the only Chaos force that features good range play is Tzeentch. The rest of the chaos troops throughout all 3 games have either a few cheap harassers or a one off unit. WoC still rely either on Marauder Horse units or the hellcannon.
I'm not familiar enough with Daemon or Chaos units to know if there's any units they could add to buff up the Four's roster. I'm honestly just happy that Tzeentch isn't wholly screwed for once.