http://ratemyserver.net/index.php?page=m...20Illusion
The thing i experienced from fighting Dark illusions in the past is pretty much that they have a huge dmg delay compared to their attack animation. Aka if you see him hit you it can take 1~3 seconds till you "see" the dmg on your HP.
Other then that, they are not to bad to take on, they take dmg from heal and are not to hard to take on other then the fact that they are boss type immune for skills.