I've also noticed this; it's happened to me twice lately, and never happened before that so I am wondering if they've introduced a bug. I'll be locked on so use retro thrusters, and while shooting forward after the back, the missile will hit me anyway... it makes no sense, I don't think it's lag because that's a fair way into the manouevre for it to hit because of that?
This actually happened to me yesterday. I know it's different from before the patch because before the patch I wouldn't take damage, whereas when this happened I died.
Of course, it could have been that I got smacked with lasers when I thought I was getting smacked with a conc. I've done that to other people, so it's possible that's what happened.
I'll keep an eye out for it and if it happens again I'll see if I can't get more details on the situation.