Holding vows are essential to Dharma practice....
That's all that needs to be said. I rest my case that simply shagging one's students and indulging in worldly pleasures to excess (to premature death!) does not make a Mahasiddha, because if it did, ordinary beings with raging attachment would be Mahasiddhas.
Well the tulkus system is very much debatable. But whether you believe in the tulku system or not, the best is to see the RESULTS. For example of Chogyam Trungpa Rinpoche, even he has 7 wives and many other affairs, we cannot deny the dharma imprints he has left on his students/wives. Many of them are are even dharma teachers now and sincere dharma practitioners.
If you have seen the video of the funeral of Chogyam Trungpa, a rainbow appeared in the clear blue sky when his body was cremated. All his students witnessed this. Definitely this is a clear sign that he is an attained being.
Many roads lead to Rome, imagine if Chogyam Trungpa had not acted the way he has had, where would these students of the 70's hippies be now? Would they still be in drugs? Overdozed? Committed suside?
We can judge based on our own perception, experience and culture, but lets take a look at the RESULTS....
Sorry to say, how would a tulku talk to a bunch of hippies? Is it by sitting on a high throne and reciting mantras and prayers? Would that work at that time? I myself think Chogyam Trungpa's method is superb, he behaved like one of his students....it is almost like a spy who infiltrated into their society in order to bring dharma at their level.
At the rate the world is degenerated where everything is about attachement, lust, jealousy and instant gratification, I believe more tulkus will manifest even more "crazy" wisdom - as appeared to our eyes- to tame the untamable.