Aoe hard CC Barbarian is dead. Though Barb, particularly pure, does get some soft aoe options: Shout, eventually Frightening Spirit Tornado.
There are items with solid trigger chances. Ball and Chain can be enchanted to trigger Prone on crit, I think. Rust's Poignard has 30% but for a long-lasting Prone, with additional damage effects built in against downed enemies. The itemization is great in general.
Trouble is, those are single target. Carnage has been nerfed badly and no longer transports weapon effects (except Lord Darryn's Voulge Static Thunder, which in Barbarian's hand causes aoe Disorient on crit and explodes accumulated Static Thunder stacks).
But there are new options. Best of them are ranged, I'm afraid.
Blunderbuss mortar weapons, which target Reflex, deal slash/pierce damage in aoe... and deliver special attacks in aoe, such as Monk Stunning Blow, but also Rogue Blinding/Confounding/Gouging Strike, Crippling/Arterial Strike, Toxic Strike DoTs and such. Even better that you can dual wield them (so 2x affliction chance, 2x crit chance, 2x resource refund chance in case of Stunning Surge)!
Rod Blast modal does this as well (but is slow).
Plus the summoned weapons that were already present in PoE1: wizard Blights, Citzal's Spirit Lance, probably also Rotskulls, but I'm not sure. With multiclassing you can combine the ability to summon such weapons with CC abilities from another class.
There are also some melee aoe weapons: Whispers of the Endless Paths GS (attacks in a cone), Wahai Poraga pollaxe (attacks up to 4 targets around, friend or foe).
And for what its worth, I think the gameplay, pacing, exploration, itemization, combat is much better in PoE2. Character building is much more involved (although classes have lost a bit of their uniqueness). Also the main town hub is incomparably better.
Thank you! You answered one of my main concerns. Carnage is no longer a CC viable option, but rather just a damage dealing ability in PoE2. That's a mighty shame