I honestly hope I make no enemies from saying my opinion on this matter.
I'm sure many of you know Manaka Sensei (x student of Hatsumi Sensei) and I must say Manaka Sensei has very good movement, but for many years he had to train alone. This is because he went into the Military and could not practice or learn from/with Hatsumi Sensei. He has stated in the past he would work continuously on Kihon Happo, Sanshin, Ukemi, and other basic techniques by himself. This is where he developed his skill, by training alone with lots of sweat and blood, nothing else.
Now of course you can hit targets and other such things, but please dont tell yourself that you must have a living opponet with you in order to practice Kihon happo, Sanshin, even Ryu Kata, thats just being lazy. And what about the few people who cannot practice every week?
Now yes there are few things that are difficult to practice alone, such as grappling techniques. This requires a very good understanding of how a human body works in order to practice alone, but it can be done.
It seems many of you are very focused on practicing the feeling of the techniques, now I am not part of the Bujinkan (though I have absolute respect for it) so I dont know your thoughts on this matter, but maybe before worrying so much about the feeling of the Kata, you should perfect each Kata to the best of your ability (low, precise, correct timing, distancing) "picture perfect" in a sense. Once you have done this, then you can add the feeling of that perticular Kata, only now you do not need to worry about the movement and doing it wrong, you only need to focous on the feeling, and if you wish, variations.
In my opinion, Kamae, Ukemi, and Kihon/Sanshin are the absolute most important things you can practice.
And if your one of the few who feel they must test themselves against other arts such as Bjj, MMA, etc. Then those 3 things, will decide the victor, not some advanced variation to some Togakure Ryu technique, or having a super deadly intent.
I apologize for my rant, but it is something I feel strongly about.
Please dont flame me to harshly, I came here to make friends and meet other people with the same interest.
Please forgive me for all my typos as well.