in the in game description of the blade barrier spell, it shows a reflex save for half damage. With the improved evasion feat, Gilli should be able to take no damage when he makes the reflex save against the spell. Normally a spell will show an improved evasion save in the chat log, and when I make the save I will take no damage. With the blade barrier spell however, it only shows a reflex save, and I take half damage still. At first I thought it was due to being a divine spell, but I tested in the arena against flame strike [being another divine spell causing divine damage] and make the imp. evasion save just fine with no damage.
I assume that this is a bug, but I could be missing something important that doesn't allow the improved evasion save to function against it.