Lately, I've played disconnecting players about as often as normal players, so I get to play the AI a lot. Actually makes me think that vs AI should just go to the database and Choose a random deck from someone with my rank.
It seems as though many players on steam use 3rd party cheat to disconnect if they don't get good openning hands. Its a reality I've just come to accept. No use in reporting them, they're probably half the player base anyway.
You don't have to use a 3rd party software to disconnect. If I wanted to do it I have a wifi on/off switch on my laptop. Also, you are correct about not bothering to report them as there is no way to tell a purposeful disconnect from an accidental one.