Are you sending in waves of demons, or just one chaotic free-for-all?
I'm just going to go down the list you provided and give my two cents. Babau: GCR 5 [Med](MM1)
- If you're going in waves, I could see 2-4 Babau being a first wave, since they're assassins, they'd likely blitz, drop the biggest threat, and then retreat once the second wave shows up. If you're going free-for-all, they don't seem like they'd fit in the army-horde mentality.Hezrou: GCR 10 [Large](MM1)
- The sergeant at arms for demons? This guy is a must include. As an EL 13, you can run him and 4 CR 8 demons or 8 CR 6s. A good ol' demon strike force sounds awesome. Vrock (x2): GCR 8 each [Large](MM1)
- They say Hezrous are the only demon to love battle more than a Vrock. And Vrocks are very iconic D&D demons. I think they'd fit well in the Hezrou platoon.Jovoc: GCR 4 [Small](MM2)
- Wow, I hadn't read these guys before. That's dirty.
I'd pair them with a bigger monster who isn't afraid to squish one in order to damage everyone in range. Kamikaze Jovocs are mean. Now I'm thinking a good wave is a Hezrou, two Vrocks, and 4-6 of these guys.Arrow Demon: GCR 6 [Med](MM3)
- Without a doubt, one of my favorite demons. Unfortunately unless you're letting a whole army through, I don't see them making the break in the first waves. I'd argue to leave them out of combat as their strength is best when they can play ranged support in a war.Carnage Demon (x5): GCR 3 each [Med](MM5)
If you're using a wave approach, a wave of carnage demons could be simple but effective. They don't use tactics or have a lot of abilities to make them more than fodder, but they may be used to soften PCs up. Depending on how many waves you want, I could see one of these, but they'd also probably be my first cut.Gadacro: GCR 2 [Small](MM5)
- These guys are pretty cool, too. But they're carrion creatures. They'd likely show up if the PCs lost, not rush through claws first.Skulvyn: GCR 3 [Large](FF)
- Unless there's a nearby rive or lake for fighting, I'd pass on the aquatic demons.Maurezhi (Advanced): GCR 10 (12 or 14 HD...) [Med](FF)
- An advanced one could be a challenge, and may even be on the front lines. More likely, I'd predict it crossed over first, took someone in town, and has been powering up, ready for the invasion.Armanite: GCR 6 [Large](FC1)
- Yes! Wow. Who summoned the cavalry? 6 of these rushing through the portal either before or after Squad Hezrou. No one's gonna enjoy that. Except maybe you. Bar-Lgura: GCR 4 [Med](FC1)
- Without time for an ambush set=up, I'd pass on these guys. Although teaming them up with Babau could make things interesting.Bulezau: GCR 8 [Large](FC1)
- Definitely. Heavy infantry of the army? Check. Terrifying looking demons? Check. I like 'em. Juvenile Nabassu (maybe an advanced one?): GCR 4+ [Med](FC1)
- Nabassu already spend part of their time on the Material Plane. Crossing over through a rift doesn't seem their style.
Well that's my two cents on the demons. If it's any help, let me know, and I'll go over the devils and Yugoloths later.