There is no difficulty setting for Special Missions and as far as I can tell it is just plain hard. This could be due to my being at a very low level with hardly any upgrades. Regardless, it is not fun to just keep dying in order to upgrade your character.
Another minus is you only get 2 AI buddies so your team is short by 1 member compared to playing multiplayer. Your AI buddies also work identically to the ones in the single-player campaign which severely limits how you can arm and use them. It does not make sense to me why the AI apothecary only has limited heal uses AND can only heal 1 person at a time when a human apothecary has unlimited uses with a cooldown timer and can heal an area as well as individuals.