One of the problems with rape cases is that it is usually one person's word against another's- which ought to be insufficient for a conviction. In the case of someone who is too drunk to consent then there is the added problem that the alleged victim's evidence is inherently flawed.
Unless of course the perpetrators are thick and arrogant enough to film themselves- like recently jailed footballer Ched Evans whose friend and brother filmed him having sex with a girl too drunk to consent (if he loves group sex that much he's going to love prison).
The victim's (who was irresponsible for getting herself paralytically drunk and alone on a night out) version of events does seem similar to other cases involving footballers, extremely drunk women and group sex where no convictions have been made. I'm not saying they're all guilty but there does seem to be a certain culture involved in the game.