If the suggestions above (and in the links / spoiler) don't help, try emailing support@larian.com, with a description of the problem and maybe a link to this topic.
Try switching to the +40% offence armour piece; if the extra defence isn't helping, maybe extra offence will let you kill memory eaters faster.
There was a bug in the unpatched version of DKS which could have certain boss opponents using an over-powered attack. I don't recall there being a similar problem in D2:ED, though.
One person in DKS who ran into this problem used CheatEngine to fix their health until they got past the problem boss (though it isn't the most user friendly program, and someone mentioned that Steam may have a problem with its use, even in a single player game).
DKS topics :
Where's the trick to Ba'al? /
[Not Sure if Bug][Spoilers]Killed InstantlyIn XP the saves are in the folder
C:\Documents and Settings\ %username% \Local Settings\Application Data\Divinity 2\Savegames
or in Vista / Win 7
C:\Users\ %username% \AppData\Local\Divinity 2\Savegames
You may need to set Windows Explorer to show hidden files and folders (
XP, Vista,
Win 7).