Thanks for confirming that I was not imagining it! I busted out the calculator and tested it in the arena, it is doing 30% as the card says it is just a display bug on the animation.
I noticed this tonight and just logged on to make this exact same message. I never got hit to verify whether it was 30 or 70 to me, but after seeing that I took it out and i'm not taking a chance until we get some official word.
How about it devs? is feint working as intended with a 70% damage trap to target and self?