Now, whenever I lay hand on the Twin I take massive amounts of damage. Flurry is nearly killing me, Dirty Fighting just takes half of my 500+ hp. The damage I take is not shown in the log and ignores my damage shields. It may not be able to kill me, as I once ended up with 2 hp, but I dont dare to try it on purpose. The last 200 hp of the twin must deal a few thousands of damage to me while I try to kill it.

EDIT: Edge adviced me to take off the ring and indeed it appeared to be the cause as I could finish the twin off without taking any damage.
Below are some screenshots from all this.
Kill spam: http://dl.dropbox.com/u/1069548/TOME/chronobug%201.png
Losing my 500 hp in one attack: http://dl.dropbox.com/u/1069548/TOME/chronobug%203.png