Single Player Skirmish Mode Good?

[BeckettColt]

So I'm thinking about picking up FA in the steam sale and I'm wondering if the single player skirmish mode is any good and if the AI is moderately challenging. I ask because my internet is epically terrible and have no doubt I wouldn't be able to play online.

Oh, and importantly, looking online I'm getting some mixed opinions on whether or not you need a connection to play even single player. Yes, I saw the topic from four years ago with this same question, but... gosh, a lots happened since then.