Generally, where an AI shines in antagonistic assistance is when it's been subverted. A malf AI cannot be controlled and is thus an incredibly unreliable element when it comes to an ally, compounded with that multi-antag role modes are the roundtype equivalent of 'Freddy vs Jason/Alien vs Predator/insert your favourite corny monster v monster movie'.
As for malf and antag AI on it's own, I've made my piece elsewhere on the subject. AIs at their core are mechanically designed to relentlessly halt and harry their opposition, no matter their status as an antag or otherwise; leading to very slow, predictable and otherwise stagnant stalemates in conflict. Little more than a tool, fitting to their lore.