They definitely didn't buff their health; when you do hit their head they still get one shot by EAT's/Quasars. I have however noticed that since the patch I will sometimes (usually when I'm not the host) shoot an enemy in a body part, hit and destroy that body part, but actually not hurt the enemy. So a headless bile titan will be running around and I need to shoot it again in the head again to get it to register. According to the other players they don't see it as headless. It might be that you're experiencing bad hit registration? This update introduced a lot of weird bugs, like the the grenade launcher grenades lose all of their momentum immediately and you can throw grenades further than it can shoot now.