Long story short, your IG have little to fear from my list, barring an unprecedented explosion of luck.
Daemon troops are generally awful, so I just go with preference. In my case, Bloodletters. I like to kill things, and they can do that in assault. I did take a Horror squad because they're cheap, but their BS 3 generally fails me. Sometimes though, their 4++ save can bog down even the most stalwart assaults. I wanted to spend even less on Troops than I did.
Both choices have the remote potential to open vehicles, which is better than the other three choices of Nurglings, Plaguebearers and Daemonettes. (Daemonettes *could* with Rending, but at T3, they never live long enough.)
Basically, my list looks something like...
Skulltaker on Juggernaut
7 Bloodcrushers
6 Fiends
6 Fiends
8 Bloodletters
8 Bloodletters
8 Bloodletters
4 Horrors & Changeling, Bolt
4 Screamers of Tzeentch
Soul Grinder, Phlegm
Soul Grinder, Phlegm
You've got enough tools to deal with all of that.
I'm just curious if it'll break me out of my general pattern of "1 win, 1 loss, 1 draw".
I'd usually take Fateweaver for his crazy fun element, but he's been throwing up all over himself lately. And with his two heads, that makes for a really big mess.
I'm one crazy spending binge away from saying, 24 Bloodcrushers, each squad led by a Herald, and Kill Main Burn!