Blocks huh? Seems like something is amiss. Divinity 2 is not bleeding edge graphically but should look quite pleasant especially on extream. Perhaps you need to update your video drivers? Out of date drivers can cause artifacting and other anomalies. Also, if they are current it might behoove you to reinstall the drivers you have. Sometimes the runtime files can get corrupted and cause the driver to malfunction.
Moreover, you might try verifying the integrity of the game cache if you purchased the game on steam. Screen shots would help if you have them. Good luck!