I noticed today that if I cast 2 feints in a row (one for each of 2 foes for example) that if an opponent attacks me both of the 30% shields break and they get the damage boost from both (2 of the same shield shouldn't break if im not mistaken) but when I cast 2 Feints on 1 opponent (they still get the 2X30%) I don't get to do 2X70% to them, I think if enemies can benefit from feint's backlash* I should benefit from a double feints damage.
TL:DR- if you cast 2X feint, an enemy can use both 30%s at once while you can't use both 70% at once.
( *for lack of better word i'm using backlash, I think there is some ability like that later though)
**Further testing I noticed I may have been mistaken and have been under a stronger level Curse spell (30% instead of Death schools 20%) and the first of the Feint attacks may have been taken without me noticing, and Curse and feint are different so it make sense they would stack.**
Please disregard unless the KI team uncovers proof as I am unable to replicate