I have noticed that when characters have been grandfathered in with their marks, the defense stat on the marks that were equipped at the time of upgrade are extremely lower than the marks held in your characters inventory. For example, I had the legendary item "Mark of a Kellslayer" equipped on my Titan. It has a defense stat of 3. However all my other legendary marks in my inventory are anywhere from 130 and up. I also received a rare mark from a quest that has a defense stat of 110. I noticed this was the case with my other two characters. This defense stat of 3 only affected mark items equipped at the time the update was installed. Hope this info helps!