I have the same issue farming leathers on the same mobs.
Have tried fresh installs with various CC's.
I assumed it was blizzards way of bot testing as if you relog you can loot the mobs again.
Ive been suspended 3 times on the one account doing this for short periods and that is how i came to the conclusion.
Each time ive had the suspension removed by stating that i couldnt loot the mobs and had to keep relogging to loot and hoped this didnt trigger the bot system.
Log file attached incase something is causing this.