On no more than 4-5 occassions the Daystars Sunray ability has caused around 1050 damage, not that i'm complaining but this seems awfully high. Any ideas as to why its like this? And yes I do have the fix patches...

Sunray is made so it has a chance to instakill undead.

Unfortunately the game is built in a way that makes undead immune to most instakill effects, so Sunray uses a "workaround" method by simply dealing so ridiculously high amounts of damage that it should put anything undead out of action instantly.