I am very late coming to this thread, but I think the changes required are more about society's attitudes than the law. There is plenty of space within the current laws for coercion, bullying and threats to be taken into account as consent under duress, rather than valid consent, I believe a court of law would consider any of these if evidence of them was brought forward.
However that doesn't change the fact that most rape victims will never take their case to a court of law, to have the facts of the matter tried. If we're using theoretical scenarios, like theft, it is the difference between scenario a) proving someone took your purse at knife-point, whilst inflicting some harm to you, leaving bruises and physical scars and scenario b) someone you invited to sleep on your sofa, took your purse (but they say you agreed to lend them the money so it's ok).
Scenario a) is provable by forensic evidence, scenario b) is about who is more convincing before the jury. Added to that, is the fact that most people in scenario b) feel embarrassed for inviting this person in and giving them the opportunity to commit their crime, thus being far less likely to report it.
I have taken a fresh look at past events in my life, viewed through the feminist perspective, and realised I have been raped (even though it is hard for me to identify myself as a rape victim). I have always been a strong, independent woman, who got her own way and did not do what men expected/wanted, which makes it far easier for me to identify as a woman who got too drunk and had some very unsatisfying, unplanned sex than someone who was raped.
It should always be an 'enthusiastic yes' and I have had several other drunken experiences (2 with people I was already friends with and 1 ONS) where I feel unequivocally consent was given, despite an actual discussion not taking place, every action was reciprocal, we kissed each other, we undressed each other, etc. The other person I got into a similar situation with (despite him being a long term friend at that stage in my life) I have always felt uncomfortable about, I can't remember the exact events so I'm not certain I didn't reciprocate his advances, but the first thing I remember (after him and another friend coming back to my flat -other friend must have left at some point) is blanking out and then being on the living room floor with him on top of me (fully clothed) and then there is another blank, next thing I remember we were naked in bed and as he was already having sex with me, it seemed too late to say no. I asked that he stopped and put a condom on, as I was more perturbed by having unprotected sex with someone, than just having unasked for, unwanted sex.
I would never have reported this to the police, as I am aware that asking him to have sex using a condom would be viewed as consent, so there would never have been any point from a legal aspect. Regardless of that, the fact we were both part of a wider friendship group, would have made it impossible for me to report. I had a boyfriend at the time, so there was a large amount of nudge, nudge, wink, wink at the guy with the cheeky smile being more appealing than the steady boyfriend (from the people who did find out - the people he boasted to), no-one who knew both of us would ever have believed it was rape and it would have been only me on trial (was I lying to cover up being unfaithful?), not just to a jury, but to everyone I knew.
I don't think the guy who did this to me ever looks at himself and feels like a rapist. Up until recently I viewed it as a 'we were both pretty drunk' moment, it is only now that I think he was considerably less drunk than I was, I have passed out/ been in similar situations with other men and woken in the morning wearing all my clothes, having not had sex with anyone, which makes me think that this was something he did to me, rather than a situation I chose to get myself into, whenever I got absolutely wasted (which I don't do anymore but used to do far too often).