Move to one of the other farmsteads - there are 4 total. Some have less casters then others, while others have small farm houses or sheds you can Line of Sight the casters into. It's good practice for looking for geometry to 'hide' behind to LoS a pull in instances, which is helpful.
I would recommend grabbing a healer and AoE farming the east farms with the Freezing Ghouls for kicks. Had me laughing for about 10 minutes