Well Im not trying to be a know-it-all but I am 100% sure that with Bio Boost you can take a melee attack because I use it on quit a few load outs. In particular my sniper load outs when I am camping and someone comes up on me and hits me I dont die. 99% of the time I still dont react fast enough to get them but I never die on the first hit...
I honestly dont know why you guys are having problems with melee... I have noticed when someone is crouched most often it takes more than a few attempts to kill with melee attacks. Often I end up crouching myself in order to get them.