This already exists. Just start a practice party with beginners welcome set. You’ll have 7 npcs to wreck mechanics with in no time.

Not only is it easy, this AI is top tier: you can converse with the bots, offer suggestions to change their behavior in aoes, and even have them appreciate your very witty one-liners.

You even get clear bonuses if you somehow manage to succeed, and the developers don’t need to waste more time creating content than they already do.