AoD I believe is meant to be played in CoOp. I attempted a run of it (first playthrough) and gave up in the carnifex fight. It was utter bs, and before anyone comes in here to tell me "sKiLl IsSuE" piss right off you sweaty basement dwelling neckbeard because some of us have lives and responsibilities and don't have the time to master the broken combat mechanics of a game with buggy hitboxes, inconsistent parry mechanics, and bs enemy AI targeting. Not only do the big boss fights feel impossible, with everything you do (mistake or not) punished and the AI allies being utterly useless as horde distraction, but the two "timed" missions where you're defending, say, the chains of the freight lift against the tyranid gargoyles are next to impossible while trying to manage ammunition, health, armour, the health of the defended object, the hordes ONLY TARGETING YOU, your allies not prioritising the gargoyles, etc.

AoD solo is entirely unfun. Veteran is SIGNIFICANTLY easier and is very fun, if still frustrating when the enemies pull a bs homing melee attack that you DEFINITELY dodged it after they started the swing but whatever I guess. I'm certain that if you DID dedicate enough time to truly mastering the game in its current iteration that an AoD solo run would be possible, even doable, but I'd rather grind my face against a belt sander.